diff --git a/.drone.jsonnet b/.drone.jsonnet
index 01c6110..6d97aa4 100644
--- a/.drone.jsonnet
+++ b/.drone.jsonnet
@@ -28,7 +28,6 @@
       'make test',
       'make test-integration',
     ],
-    depends_on: ["gomod"]
   },
 
   steps: [
@@ -43,7 +42,7 @@
     build('1.11'),
     build('1.12'),
     build('1.13'),
-    build('1.14-rc') + {depends_on: ["build-1.11", "build-1.12", "build-1.13"]},
+    build('1.14-rc'),
 
     golang() {
       name: 'generate',
@@ -52,7 +51,6 @@
         'make generate',
         'git diff --exit-code',
       ],
-      depends_on: ["build-1.13"]
     },
   ],
 }
diff --git a/.drone.yml b/.drone.yml
index 9641363..22c5086 100644
--- a/.drone.yml
+++ b/.drone.yml
@@ -35,8 +35,6 @@ steps:
     event:
       exclude:
       - tag
-  depends_on:
-  - gomod
 
 - name: build-1.12
   pull: always
@@ -52,8 +50,6 @@ steps:
     event:
       exclude:
       - tag
-  depends_on:
-  - gomod
 
 - name: build-1.13
   pull: always
@@ -69,8 +65,6 @@ steps:
     event:
       exclude:
       - tag
-  depends_on:
-  - gomod
 
 - name: build-1.14-rc
   pull: always
@@ -86,10 +80,6 @@ steps:
     event:
       exclude:
       - tag
-  depends_on:
-  - build-1.11
-  - build-1.12
-  - build-1.13
 
 - name: generate
   pull: always
@@ -105,7 +95,5 @@ steps:
     event:
       exclude:
       - tag
-  depends_on:
-  - build-1.13
 
 ...
diff --git a/cmd/jb/init.go b/cmd/jb/init.go
index 0e7a56a..2f7be4c 100644
--- a/cmd/jb/init.go
+++ b/cmd/jb/init.go
@@ -19,10 +19,10 @@ import (
 	"io/ioutil"
 	"path/filepath"
 
-	kingpin "gopkg.in/alecthomas/kingpin.v2"
+	"gopkg.in/alecthomas/kingpin.v2"
 
 	"github.com/jsonnet-bundler/jsonnet-bundler/pkg/jsonnetfile"
-	"github.com/jsonnet-bundler/jsonnet-bundler/spec"
+	v1 "github.com/jsonnet-bundler/jsonnet-bundler/spec/v1"
 )
 
 func initCommand(dir string) int {
@@ -34,7 +34,7 @@ func initCommand(dir string) int {
 		return 1
 	}
 
-	s := spec.New()
+	s := v1.New()
 	// TODO: disable them by default eventually
 	// s.LegacyImports = false
 
diff --git a/cmd/jb/install.go b/cmd/jb/install.go
index e4c4605..292b92d 100644
--- a/cmd/jb/install.go
+++ b/cmd/jb/install.go
@@ -22,12 +22,12 @@ import (
 	"reflect"
 
 	"github.com/pkg/errors"
-	kingpin "gopkg.in/alecthomas/kingpin.v2"
+	"gopkg.in/alecthomas/kingpin.v2"
 
 	"github.com/jsonnet-bundler/jsonnet-bundler/pkg"
 	"github.com/jsonnet-bundler/jsonnet-bundler/pkg/jsonnetfile"
-	"github.com/jsonnet-bundler/jsonnet-bundler/spec"
-	"github.com/jsonnet-bundler/jsonnet-bundler/spec/deps"
+	v1 "github.com/jsonnet-bundler/jsonnet-bundler/spec/v1"
+	"github.com/jsonnet-bundler/jsonnet-bundler/spec/v1/deps"
 )
 
 func installCommand(dir, jsonnetHome string, uris []string) int {
@@ -78,7 +78,7 @@ func installCommand(dir, jsonnetHome string, uris []string) int {
 		"updating jsonnetfile.json")
 
 	kingpin.FatalIfError(
-		writeChangedJsonnetFile(jblockfilebytes, &spec.JsonnetFile{Dependencies: locked}, filepath.Join(dir, jsonnetfile.LockFile)),
+		writeChangedJsonnetFile(jblockfilebytes, &v1.JsonnetFile{Dependencies: locked}, filepath.Join(dir, jsonnetfile.LockFile)),
 		"updating jsonnetfile.lock.json")
 
 	return 0
@@ -102,7 +102,7 @@ func writeJSONFile(name string, d interface{}) error {
 	return ioutil.WriteFile(name, b, 0644)
 }
 
-func writeChangedJsonnetFile(originalBytes []byte, modified *spec.JsonnetFile, path string) error {
+func writeChangedJsonnetFile(originalBytes []byte, modified *v1.JsonnetFile, path string) error {
 	origJsonnetFile, err := jsonnetfile.Unmarshal(originalBytes)
 	if err != nil {
 		return err
diff --git a/cmd/jb/install_test.go b/cmd/jb/install_test.go
index 81160cc..894c6ea 100644
--- a/cmd/jb/install_test.go
+++ b/cmd/jb/install_test.go
@@ -24,12 +24,11 @@ import (
 	"github.com/stretchr/testify/assert"
 
 	"github.com/jsonnet-bundler/jsonnet-bundler/pkg/jsonnetfile"
-	"github.com/jsonnet-bundler/jsonnet-bundler/spec"
-	"github.com/jsonnet-bundler/jsonnet-bundler/spec/deps"
+	v1 "github.com/jsonnet-bundler/jsonnet-bundler/spec/v1"
+	"github.com/jsonnet-bundler/jsonnet-bundler/spec/v1/deps"
 )
 
-// TODO: Change legacyImports to false eventually
-const initContents = `{"dependencies": [], "legacyImports": true}`
+const initContents = `{"version": 1, "dependencies": [], "legacyImports": false}`
 
 func TestInstallCommand(t *testing.T) {
 	testInstallCommandWithJsonnetHome(t, "vendor")
@@ -60,15 +59,15 @@ func testInstallCommandWithJsonnetHome(t *testing.T, jsonnetHome string) {
 			Name:                    "OneURL",
 			URIs:                    []string{"github.com/jsonnet-bundler/jsonnet-bundler@v0.1.0"},
 			ExpectedCode:            0,
-			ExpectedJsonnetFile:     []byte(`{"dependencies": [{"source": {"git": {"remote": "https://github.com/jsonnet-bundler/jsonnet-bundler", "subdir": ""}}, "version": "v0.1.0"}], "legacyImports": true}`),
-			ExpectedJsonnetLockFile: []byte(`{"dependencies": [{"source": {"git": {"remote": "https://github.com/jsonnet-bundler/jsonnet-bundler", "subdir": ""}}, "version": "080f157c7fb85ad0281ea78f6c641eaa570a582f", "sum": "W1uI550rQ66axRpPXA2EZDquyPg/5PHZlvUz1NEzefg="}], "legacyImports": false}`),
+			ExpectedJsonnetFile:     []byte(`{"version": 1, "dependencies": [{"source": {"git": {"remote": "https://github.com/jsonnet-bundler/jsonnet-bundler", "subdir": ""}}, "version": "v0.1.0"}], "legacyImports": false}`),
+			ExpectedJsonnetLockFile: []byte(`{"version": 1, "dependencies": [{"source": {"git": {"remote": "https://github.com/jsonnet-bundler/jsonnet-bundler", "subdir": ""}}, "version": "080f157c7fb85ad0281ea78f6c641eaa570a582f", "sum": "W1uI550rQ66axRpPXA2EZDquyPg/5PHZlvUz1NEzefg="}], "legacyImports": false}`),
 		},
 		{
 			Name:                    "Local",
 			URIs:                    []string{"jsonnet/foobar"},
 			ExpectedCode:            0,
-			ExpectedJsonnetFile:     []byte(`{"dependencies": [{"source": {"local": {"directory": "jsonnet/foobar"}}, "version": ""}], "legacyImports": true}`),
-			ExpectedJsonnetLockFile: []byte(`{"dependencies": [{"source": {"local": {"directory": "jsonnet/foobar"}}, "version": ""}], "legacyImports": false}`),
+			ExpectedJsonnetFile:     []byte(`{"version": 1, "dependencies": [{"source": {"local": {"directory": "jsonnet/foobar"}}, "version": ""}], "legacyImports": false}`),
+			ExpectedJsonnetLockFile: []byte(`{"version": 1, "dependencies": [{"source": {"local": {"directory": "jsonnet/foobar"}}, "version": ""}], "legacyImports": false}`),
 		},
 	}
 
@@ -118,19 +117,19 @@ func TestWriteChangedJsonnetFile(t *testing.T) {
 	testcases := []struct {
 		Name             string
 		JsonnetFileBytes []byte
-		NewJsonnetFile   spec.JsonnetFile
+		NewJsonnetFile   v1.JsonnetFile
 		ExpectWrite      bool
 	}{
 		{
 			Name:             "NoDiffEmpty",
 			JsonnetFileBytes: []byte(`{}`),
-			NewJsonnetFile:   spec.New(),
+			NewJsonnetFile:   v1.New(),
 			ExpectWrite:      false,
 		},
 		{
 			Name:             "NoDiffNotEmpty",
 			JsonnetFileBytes: []byte(`{"dependencies": [{"version": "master"}]}`),
-			NewJsonnetFile: spec.JsonnetFile{
+			NewJsonnetFile: v1.JsonnetFile{
 				Dependencies: map[string]deps.Dependency{
 					"": {
 						Version: "master",
@@ -142,7 +141,7 @@ func TestWriteChangedJsonnetFile(t *testing.T) {
 		{
 			Name:             "DiffVersion",
 			JsonnetFileBytes: []byte(`{"dependencies": [{"version": "1.0"}]}`),
-			NewJsonnetFile: spec.JsonnetFile{
+			NewJsonnetFile: v1.JsonnetFile{
 				Dependencies: map[string]deps.Dependency{
 					"": {
 						Version: "2.0",
@@ -154,7 +153,7 @@ func TestWriteChangedJsonnetFile(t *testing.T) {
 		{
 			Name:             "Diff",
 			JsonnetFileBytes: []byte(`{}`),
-			NewJsonnetFile: spec.JsonnetFile{
+			NewJsonnetFile: v1.JsonnetFile{
 				Dependencies: map[string]deps.Dependency{
 					"github.com/foobar/foobar": {
 						Source: deps.Source{
diff --git a/cmd/jb/main_test.go b/cmd/jb/main_test.go
index 3e1e1de..91346fb 100644
--- a/cmd/jb/main_test.go
+++ b/cmd/jb/main_test.go
@@ -20,7 +20,7 @@ import (
 
 	"github.com/stretchr/testify/assert"
 
-	"github.com/jsonnet-bundler/jsonnet-bundler/spec/deps"
+	"github.com/jsonnet-bundler/jsonnet-bundler/spec/v1/deps"
 )
 
 func TestParseDependency(t *testing.T) {
diff --git a/cmd/jb/update.go b/cmd/jb/update.go
index e8623aa..f339782 100644
--- a/cmd/jb/update.go
+++ b/cmd/jb/update.go
@@ -19,12 +19,12 @@ import (
 	"os"
 	"path/filepath"
 
-	kingpin "gopkg.in/alecthomas/kingpin.v2"
+	"gopkg.in/alecthomas/kingpin.v2"
 
 	"github.com/jsonnet-bundler/jsonnet-bundler/pkg"
 	"github.com/jsonnet-bundler/jsonnet-bundler/pkg/jsonnetfile"
-	"github.com/jsonnet-bundler/jsonnet-bundler/spec"
-	"github.com/jsonnet-bundler/jsonnet-bundler/spec/deps"
+	v1 "github.com/jsonnet-bundler/jsonnet-bundler/spec/v1"
+	"github.com/jsonnet-bundler/jsonnet-bundler/spec/v1/deps"
 )
 
 func updateCommand(dir, jsonnetHome string, urls ...*url.URL) int {
@@ -48,7 +48,7 @@ func updateCommand(dir, jsonnetHome string, urls ...*url.URL) int {
 		writeJSONFile(filepath.Join(dir, jsonnetfile.File), jsonnetFile),
 		"updating jsonnetfile.json")
 	kingpin.FatalIfError(
-		writeJSONFile(filepath.Join(dir, jsonnetfile.LockFile), spec.JsonnetFile{Dependencies: locked}),
+		writeJSONFile(filepath.Join(dir, jsonnetfile.LockFile), v1.JsonnetFile{Dependencies: locked}),
 		"updating jsonnetfile.lock.json")
 	return 0
 }
diff --git a/pkg/git.go b/pkg/git.go
index 7427a17..26d20d3 100644
--- a/pkg/git.go
+++ b/pkg/git.go
@@ -33,7 +33,7 @@ import (
 	"github.com/fatih/color"
 	"github.com/pkg/errors"
 
-	"github.com/jsonnet-bundler/jsonnet-bundler/spec/deps"
+	"github.com/jsonnet-bundler/jsonnet-bundler/spec/v1/deps"
 )
 
 type GitPackage struct {
diff --git a/pkg/jsonnetfile/jsonnetfile.go b/pkg/jsonnetfile/jsonnetfile.go
index 3022e8a..a576b5e 100644
--- a/pkg/jsonnetfile/jsonnetfile.go
+++ b/pkg/jsonnetfile/jsonnetfile.go
@@ -21,8 +21,9 @@ import (
 
 	"github.com/pkg/errors"
 
-	"github.com/jsonnet-bundler/jsonnet-bundler/spec"
-	"github.com/jsonnet-bundler/jsonnet-bundler/spec/deps"
+	v0 "github.com/jsonnet-bundler/jsonnet-bundler/spec/v0"
+	v1 "github.com/jsonnet-bundler/jsonnet-bundler/spec/v1"
+	depsv1 "github.com/jsonnet-bundler/jsonnet-bundler/spec/v1/deps"
 )
 
 const (
@@ -30,13 +31,15 @@ const (
 	LockFile = "jsonnetfile.lock.json"
 )
 
-var ErrNoFile = errors.New("no jsonnetfile")
+var (
+	ErrUpdateJB = errors.New("jsonnetfile version unknown, update jb")
+)
 
 // Load reads a jsonnetfile.(lock).json from disk
-func Load(filepath string) (spec.JsonnetFile, error) {
+func Load(filepath string) (v1.JsonnetFile, error) {
 	bytes, err := ioutil.ReadFile(filepath)
 	if err != nil {
-		return spec.New(), err
+		return v1.New(), err
 	}
 
 	return Unmarshal(bytes)
@@ -44,19 +47,56 @@ func Load(filepath string) (spec.JsonnetFile, error) {
 
 // Unmarshal creates a spec.JsonnetFile from bytes. Empty bytes
 // will create an empty spec.
-func Unmarshal(bytes []byte) (spec.JsonnetFile, error) {
-	m := spec.New()
+func Unmarshal(bytes []byte) (v1.JsonnetFile, error) {
+	m := v1.New()
+
 	if len(bytes) == 0 {
 		return m, nil
 	}
-	if err := json.Unmarshal(bytes, &m); err != nil {
-		return m, errors.Wrap(err, "failed to unmarshal file")
-	}
-	if m.Dependencies == nil {
-		m.Dependencies = make(map[string]deps.Dependency)
+
+	versions := struct {
+		Version uint `json:"version"`
+	}{}
+
+	err := json.Unmarshal(bytes, &versions)
+	if err != nil {
+		return m, err
 	}
 
-	return m, nil
+	if versions.Version > v1.Version {
+		return m, ErrUpdateJB
+	}
+
+	if versions.Version == v1.Version {
+		if err := json.Unmarshal(bytes, &m); err != nil {
+			return m, errors.Wrap(err, "failed to unmarshal v1 file")
+		}
+
+		return m, nil
+	} else {
+		var mv0 v0.JsonnetFile
+		if err := json.Unmarshal(bytes, &mv0); err != nil {
+			return m, errors.Wrap(err, "failed to unmarshal jsonnetfile")
+		}
+
+		for name, dep := range mv0.Dependencies {
+			var d depsv1.Dependency
+			if dep.Source.GitSource != nil {
+				d = *depsv1.Parse("", dep.Source.GitSource.Remote)
+				d.Source.GitSource.Subdir = dep.Source.GitSource.Subdir
+			}
+			if dep.Source.LocalSource != nil {
+				d = *depsv1.Parse(dep.Source.LocalSource.Directory, dep.Source.GitSource.Remote)
+			}
+
+			d.Sum = dep.Sum
+			d.Version = dep.Version
+
+			m.Dependencies[name] = d
+		}
+
+		return m, nil
+	}
 }
 
 // Exists returns whether the file at the given path exists
diff --git a/pkg/jsonnetfile/jsonnetfile_test.go b/pkg/jsonnetfile/jsonnetfile_test.go
index dfe655f..ad1afcf 100644
--- a/pkg/jsonnetfile/jsonnetfile_test.go
+++ b/pkg/jsonnetfile/jsonnetfile_test.go
@@ -23,47 +23,167 @@ import (
 	"github.com/stretchr/testify/assert"
 
 	"github.com/jsonnet-bundler/jsonnet-bundler/pkg/jsonnetfile"
-	"github.com/jsonnet-bundler/jsonnet-bundler/spec"
-	"github.com/jsonnet-bundler/jsonnet-bundler/spec/deps"
+	v1 "github.com/jsonnet-bundler/jsonnet-bundler/spec/v1"
+	"github.com/jsonnet-bundler/jsonnet-bundler/spec/v1/deps"
 )
 
 const notExist = "/this/does/not/exist"
 
-func TestLoad(t *testing.T) {
-	jsonnetfileContent := `
-{
-    "legacyImports": false,
-    "dependencies": [
-        {
-            "source": {
-                "git": {
-                    "remote": "https://github.com/foobar/foobar",
-                    "subdir": ""
-                }
-            },
-            "version": "master"
+const v0JSON = `{
+  "dependencies": [
+    {
+      "name": "grafana-builder",
+      "source": {
+        "git": {
+          "remote": "https://github.com/grafana/jsonnet-libs",
+          "subdir": "grafana-builder"
         }
-    ]
-}
-`
+      },
+      "version": "54865853ebc1f901964e25a2e7a0e4d2cb6b9648",
+      "sum": "ELsYwK+kGdzX1mee2Yy+/b2mdO4Y503BOCDkFzwmGbE="
+    },
+    {
+      "name": "prometheus-mixin",
+      "source": {
+        "git": {
+          "remote": "https://github.com/prometheus/prometheus",
+          "subdir": "documentation/prometheus-mixin"
+        }
+      },
+      "version": "7c039a6b3b4b2a9d7c613ac8bd3fc16e8ca79684",
+      "sum": "bVGOsq3hLOw2irNPAS91a5dZJqQlBUNWy3pVwM4+kIY="
+    }
+  ]
+}`
 
-	jsonnetFileExpected := spec.JsonnetFile{
-		LegacyImports: false,
-		Dependencies: map[string]deps.Dependency{
-			"github.com/foobar/foobar": {
-				Source: deps.Source{
-					GitSource: &deps.Git{
-						Scheme: deps.GitSchemeHTTPS,
-						Host:   "github.com",
-						User:   "foobar",
-						Repo:   "foobar",
-						Subdir: "",
-					},
+var v0Jsonnetfile = v1.JsonnetFile{
+	Dependencies: map[string]deps.Dependency{
+		"grafana-builder": {
+			Source: deps.Source{
+				GitSource: &deps.Git{
+					Scheme: deps.GitSchemeHTTPS,
+					Host:   "github.com",
+					User:   "grafana",
+					Repo:   "jsonnet-libs",
+					Subdir: "grafana-builder",
 				},
-				Version: "master",
-			}},
+			},
+			Version: "54865853ebc1f901964e25a2e7a0e4d2cb6b9648",
+			Sum:     "ELsYwK+kGdzX1mee2Yy+/b2mdO4Y503BOCDkFzwmGbE=",
+		},
+		"prometheus-mixin": {
+			Source: deps.Source{
+				GitSource: &deps.Git{
+					Scheme: deps.GitSchemeHTTPS,
+					Host:   "github.com",
+					User:   "prometheus",
+					Repo:   "prometheus",
+					Subdir: "documentation/prometheus-mixin",
+				},
+			},
+			Version: "7c039a6b3b4b2a9d7c613ac8bd3fc16e8ca79684",
+			Sum:     "bVGOsq3hLOw2irNPAS91a5dZJqQlBUNWy3pVwM4+kIY=",
+		},
+	},
+	LegacyImports: true,
+}
+
+const v1JSON = `{
+  "version": 1,
+  "dependencies": [
+    {
+      "source": {
+        "git": {
+          "remote": "https://github.com/grafana/jsonnet-libs",
+          "subdir": "grafana-builder"
+        }
+      },
+      "version": "54865853ebc1f901964e25a2e7a0e4d2cb6b9648",
+      "sum": "ELsYwK+kGdzX1mee2Yy+/b2mdO4Y503BOCDkFzwmGbE="
+    },
+    {
+      "name": "prometheus",
+      "source": {
+        "git": {
+          "remote": "https://github.com/prometheus/prometheus",
+          "subdir": "documentation/prometheus-mixin"
+        }
+      },
+      "version": "7c039a6b3b4b2a9d7c613ac8bd3fc16e8ca79684",
+      "sum": "bVGOsq3hLOw2irNPAS91a5dZJqQlBUNWy3pVwM4+kIY="
+    }
+  ],
+  "legacyImports": false
+}`
+
+var v1Jsonnetfile = v1.JsonnetFile{
+	Dependencies: map[string]deps.Dependency{
+		"github.com/grafana/jsonnet-libs/grafana-builder": {
+			Source: deps.Source{
+				GitSource: &deps.Git{
+					Scheme: deps.GitSchemeHTTPS,
+					Host:   "github.com",
+					User:   "grafana",
+					Repo:   "jsonnet-libs",
+					Subdir: "/grafana-builder",
+				},
+			},
+			Version: "54865853ebc1f901964e25a2e7a0e4d2cb6b9648",
+			Sum:     "ELsYwK+kGdzX1mee2Yy+/b2mdO4Y503BOCDkFzwmGbE=",
+		},
+		"github.com/prometheus/prometheus/documentation/prometheus-mixin": {
+			LegacyNameCompat: "prometheus",
+			Source: deps.Source{
+				GitSource: &deps.Git{
+					Scheme: deps.GitSchemeHTTPS,
+					Host:   "github.com",
+					User:   "prometheus",
+					Repo:   "prometheus",
+					Subdir: "/documentation/prometheus-mixin",
+				},
+			},
+			Version: "7c039a6b3b4b2a9d7c613ac8bd3fc16e8ca79684",
+			Sum:     "bVGOsq3hLOw2irNPAS91a5dZJqQlBUNWy3pVwM4+kIY=",
+		},
+	},
+	LegacyImports: false,
+}
+
+func TestVersions(t *testing.T) {
+	tests := []struct {
+		Name        string
+		JSON        string
+		Jsonnetfile v1.JsonnetFile
+		Error       error
+	}{
+		{
+			Name:        "v0",
+			JSON:        v0JSON,
+			Jsonnetfile: v0Jsonnetfile,
+		},
+		{
+			Name:        "v1",
+			JSON:        v1JSON,
+			Jsonnetfile: v1Jsonnetfile,
+		},
+		{
+			Name:        "v100",
+			JSON:        `{"version": 100}`,
+			Jsonnetfile: v1.New(),
+			Error:       jsonnetfile.ErrUpdateJB,
+		},
 	}
 
+	for _, tc := range tests {
+		t.Run(tc.Name, func(t *testing.T) {
+			jf, err := jsonnetfile.Unmarshal([]byte(tc.JSON))
+			assert.Equal(t, tc.Error, err)
+			assert.Equal(t, tc.Jsonnetfile, jf)
+		})
+	}
+}
+
+func TestLoadV1(t *testing.T) {
 	tempDir, err := ioutil.TempDir("", "jb-load-jsonnetfile")
 	if err != nil {
 		t.Fatal(err)
@@ -71,12 +191,12 @@ func TestLoad(t *testing.T) {
 	defer os.RemoveAll(tempDir)
 
 	tempFile := filepath.Join(tempDir, jsonnetfile.File)
-	err = ioutil.WriteFile(tempFile, []byte(jsonnetfileContent), os.ModePerm)
+	err = ioutil.WriteFile(tempFile, []byte(v1JSON), os.ModePerm)
 	assert.Nil(t, err)
 
 	jf, err := jsonnetfile.Load(tempFile)
 	assert.Nil(t, err)
-	assert.Equal(t, jsonnetFileExpected, jf)
+	assert.Equal(t, v1Jsonnetfile, jf)
 }
 
 func TestLoadEmpty(t *testing.T) {
@@ -88,18 +208,18 @@ func TestLoadEmpty(t *testing.T) {
 
 	// write empty json file
 	tempFile := filepath.Join(tempDir, jsonnetfile.File)
-	err = ioutil.WriteFile(tempFile, []byte(`{}`), os.ModePerm)
+	err = ioutil.WriteFile(tempFile, []byte(`{"version":1}`), os.ModePerm)
 	assert.Nil(t, err)
 
 	// expect it to be loaded properly
 	got, err := jsonnetfile.Load(tempFile)
 	assert.Nil(t, err)
-	assert.Equal(t, spec.New(), got)
+	assert.Equal(t, v1.New(), got)
 }
 
 func TestLoadNotExist(t *testing.T) {
 	jf, err := jsonnetfile.Load(notExist)
-	assert.Equal(t, spec.New(), jf)
+	assert.Equal(t, v1.New(), jf)
 	assert.Error(t, err)
 }
 
diff --git a/pkg/local.go b/pkg/local.go
index f91b1bc..d91d733 100644
--- a/pkg/local.go
+++ b/pkg/local.go
@@ -21,7 +21,7 @@ import (
 
 	"github.com/pkg/errors"
 
-	"github.com/jsonnet-bundler/jsonnet-bundler/spec/deps"
+	"github.com/jsonnet-bundler/jsonnet-bundler/spec/v1/deps"
 )
 
 type LocalPackage struct {
diff --git a/pkg/packages.go b/pkg/packages.go
index d02984c..63f521d 100644
--- a/pkg/packages.go
+++ b/pkg/packages.go
@@ -28,8 +28,8 @@ import (
 	"github.com/pkg/errors"
 
 	"github.com/jsonnet-bundler/jsonnet-bundler/pkg/jsonnetfile"
-	"github.com/jsonnet-bundler/jsonnet-bundler/spec"
-	"github.com/jsonnet-bundler/jsonnet-bundler/spec/deps"
+	v1 "github.com/jsonnet-bundler/jsonnet-bundler/spec/v1"
+	"github.com/jsonnet-bundler/jsonnet-bundler/spec/v1/deps"
 )
 
 var (
@@ -49,7 +49,7 @@ var (
 //
 // Finally, all unknown files and directories are removed from vendor/
 // The full list of locked depedencies is returned
-func Ensure(direct spec.JsonnetFile, vendorDir string, oldLocks map[string]deps.Dependency) (map[string]deps.Dependency, error) {
+func Ensure(direct v1.JsonnetFile, vendorDir string, oldLocks map[string]deps.Dependency) (map[string]deps.Dependency, error) {
 	// ensure all required files are in vendor
 	// This is the actual installation
 	locks, err := ensure(direct.Dependencies, vendorDir, oldLocks)
diff --git a/pkg/packages_test.go b/pkg/packages_test.go
index 8c025b3..1319475 100644
--- a/pkg/packages_test.go
+++ b/pkg/packages_test.go
@@ -17,7 +17,7 @@ package pkg
 import (
 	"testing"
 
-	"github.com/jsonnet-bundler/jsonnet-bundler/spec/deps"
+	"github.com/jsonnet-bundler/jsonnet-bundler/spec/v1/deps"
 )
 
 func TestKnown(t *testing.T) {
diff --git a/spec/v0/spec.go b/spec/v0/spec.go
new file mode 100644
index 0000000..6d1bf2c
--- /dev/null
+++ b/spec/v0/spec.go
@@ -0,0 +1,89 @@
+// Copyright 2018 jsonnet-bundler authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package spec
+
+import (
+	"encoding/json"
+	"sort"
+)
+
+// JsonnetFile is the structure of a `.json` file describing a set of jsonnet
+// dependencies. It is used for both, the jsonnetFile and the lockFile.
+type JsonnetFile struct {
+	Dependencies map[string]Dependency
+}
+
+// New returns a new JsonnetFile with the dependencies map initialized
+func New() JsonnetFile {
+	return JsonnetFile{
+		Dependencies: make(map[string]Dependency),
+	}
+}
+
+// jsonFile is the json representation of a JsonnetFile, which is different for
+// compatibility reasons.
+type jsonFile struct {
+	Dependencies []Dependency `json:"dependencies"`
+}
+
+// UnmarshalJSON unmarshals a `jsonFile`'s json into a JsonnetFile
+func (jf *JsonnetFile) UnmarshalJSON(data []byte) error {
+	var s jsonFile
+	if err := json.Unmarshal(data, &s); err != nil {
+		return err
+	}
+
+	jf.Dependencies = make(map[string]Dependency)
+	for _, d := range s.Dependencies {
+		jf.Dependencies[d.Name] = d
+	}
+	return nil
+}
+
+// MarshalJSON serializes a JsonnetFile into json of the format of a `jsonFile`
+func (jf JsonnetFile) MarshalJSON() ([]byte, error) {
+	var s jsonFile
+	for _, d := range jf.Dependencies {
+		s.Dependencies = append(s.Dependencies, d)
+	}
+
+	sort.SliceStable(s.Dependencies, func(i int, j int) bool {
+		return s.Dependencies[i].Name < s.Dependencies[j].Name
+	})
+
+	return json.Marshal(s)
+}
+
+type Dependency struct {
+	Name      string `json:"name"`
+	Source    Source `json:"source"`
+	Version   string `json:"version"`
+	Sum       string `json:"sum,omitempty"`
+	DepSource string `json:"-"`
+}
+
+type Source struct {
+	GitSource   *GitSource   `json:"git,omitempty"`
+	LocalSource *LocalSource `json:"local,omitempty"`
+}
+
+type GitSource struct {
+	Remote string `json:"remote"`
+	Subdir string `json:"subdir"`
+}
+
+type LocalSource struct {
+	Directory string `json:"directory"`
+}
diff --git a/spec/v0/spec_test.go b/spec/v0/spec_test.go
new file mode 100644
index 0000000..3b7607f
--- /dev/null
+++ b/spec/v0/spec_test.go
@@ -0,0 +1,109 @@
+// Copyright 2018 jsonnet-bundler authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package spec
+
+import (
+	"encoding/json"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+const jsonJF = `{
+  "dependencies": [
+    {
+      "name": "grafana-builder",
+      "source": {
+        "git": {
+          "remote": "https://github.com/grafana/jsonnet-libs",
+          "subdir": "grafana-builder"
+        }
+      },
+      "version": "54865853ebc1f901964e25a2e7a0e4d2cb6b9648",
+      "sum": "ELsYwK+kGdzX1mee2Yy+/b2mdO4Y503BOCDkFzwmGbE="
+    },
+    {
+      "name": "prometheus-mixin",
+      "source": {
+        "git": {
+          "remote": "https://github.com/prometheus/prometheus",
+          "subdir": "documentation/prometheus-mixin"
+        }
+      },
+      "version": "7c039a6b3b4b2a9d7c613ac8bd3fc16e8ca79684",
+      "sum": "bVGOsq3hLOw2irNPAS91a5dZJqQlBUNWy3pVwM4+kIY="
+    }
+  ]
+}`
+
+func testData() JsonnetFile {
+	return JsonnetFile{
+		Dependencies: map[string]Dependency{
+			"grafana-builder": {
+				Name: "grafana-builder",
+				Source: Source{
+					GitSource: &GitSource{
+						Remote: "https://github.com/grafana/jsonnet-libs",
+						Subdir: "grafana-builder",
+					},
+				},
+				Version: "54865853ebc1f901964e25a2e7a0e4d2cb6b9648",
+				Sum:     "ELsYwK+kGdzX1mee2Yy+/b2mdO4Y503BOCDkFzwmGbE=",
+			},
+			"prometheus-mixin": {
+				Name: "prometheus-mixin",
+				Source: Source{
+					GitSource: &GitSource{
+						Remote: "https://github.com/prometheus/prometheus",
+						Subdir: "documentation/prometheus-mixin",
+					},
+				},
+				Version: "7c039a6b3b4b2a9d7c613ac8bd3fc16e8ca79684",
+				Sum:     "bVGOsq3hLOw2irNPAS91a5dZJqQlBUNWy3pVwM4+kIY=",
+			},
+		},
+	}
+}
+
+// TestUnmarshal checks that unmarshalling works
+func TestUnmarshal(t *testing.T) {
+	var dst JsonnetFile
+	err := json.Unmarshal([]byte(jsonJF), &dst)
+	require.NoError(t, err)
+	assert.Equal(t, testData(), dst)
+}
+
+// TestMarshal checks that marshalling works
+func TestMarshal(t *testing.T) {
+	data, err := json.Marshal(testData())
+	require.NoError(t, err)
+	assert.JSONEq(t, jsonJF, string(data))
+}
+
+// TestRemarshal checks that unmarshalling a previously marshalled object yields
+// the same object
+func TestRemarshal(t *testing.T) {
+	jf := testData()
+
+	data, err := json.Marshal(jf)
+	require.NoError(t, err)
+
+	var dst JsonnetFile
+	err = json.Unmarshal(data, &dst)
+	require.NoError(t, err)
+
+	assert.Equal(t, jf, dst)
+}
diff --git a/spec/deps/dependencies.go b/spec/v1/deps/dependencies.go
similarity index 100%
rename from spec/deps/dependencies.go
rename to spec/v1/deps/dependencies.go
diff --git a/spec/deps/dependencies_test.go b/spec/v1/deps/dependencies_test.go
similarity index 100%
rename from spec/deps/dependencies_test.go
rename to spec/v1/deps/dependencies_test.go
diff --git a/spec/deps/git.go b/spec/v1/deps/git.go
similarity index 100%
rename from spec/deps/git.go
rename to spec/v1/deps/git.go
diff --git a/spec/deps/git_test.go b/spec/v1/deps/git_test.go
similarity index 100%
rename from spec/deps/git_test.go
rename to spec/v1/deps/git_test.go
diff --git a/spec/spec.go b/spec/v1/spec.go
similarity index 93%
rename from spec/spec.go
rename to spec/v1/spec.go
index d24359e..a83b9cb 100644
--- a/spec/spec.go
+++ b/spec/v1/spec.go
@@ -18,9 +18,11 @@ import (
 	"encoding/json"
 	"sort"
 
-	"github.com/jsonnet-bundler/jsonnet-bundler/spec/deps"
+	"github.com/jsonnet-bundler/jsonnet-bundler/spec/v1/deps"
 )
 
+const Version uint = 1
+
 // JsonnetFile is the structure of a `.json` file describing a set of jsonnet
 // dependencies. It is used for both, the jsonnetFile and the lockFile.
 type JsonnetFile struct {
@@ -42,6 +44,7 @@ func New() JsonnetFile {
 // jsonFile is the json representation of a JsonnetFile, which is different for
 // compatibility reasons.
 type jsonFile struct {
+	Version       uint              `json:"version"`
 	Dependencies  []deps.Dependency `json:"dependencies"`
 	LegacyImports bool              `json:"legacyImports"`
 }
@@ -59,14 +62,18 @@ func (jf *JsonnetFile) UnmarshalJSON(data []byte) error {
 	for _, d := range s.Dependencies {
 		jf.Dependencies[d.Name()] = d
 	}
+
 	jf.LegacyImports = s.LegacyImports
+
 	return nil
 }
 
 // MarshalJSON serializes a JsonnetFile into json of the format of a `jsonFile`
 func (jf JsonnetFile) MarshalJSON() ([]byte, error) {
 	var s jsonFile
-	s.LegacyImports = jf.LegacyImports
+
+	s.Version = Version
+
 	for _, d := range jf.Dependencies {
 		s.Dependencies = append(s.Dependencies, d)
 	}
diff --git a/spec/spec_test.go b/spec/v1/spec_test.go
similarity index 97%
rename from spec/spec_test.go
rename to spec/v1/spec_test.go
index 02dc9de..73c3353 100644
--- a/spec/spec_test.go
+++ b/spec/v1/spec_test.go
@@ -18,12 +18,14 @@ import (
 	"encoding/json"
 	"testing"
 
-	"github.com/jsonnet-bundler/jsonnet-bundler/spec/deps"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
+
+	"github.com/jsonnet-bundler/jsonnet-bundler/spec/v1/deps"
 )
 
 const jsonJF = `{
+  "version": 1,
   "dependencies": [
     {
       "source": {
diff --git a/tool/rewrite/rewrite.go b/tool/rewrite/rewrite.go
index 3fc31d0..0e07c0c 100644
--- a/tool/rewrite/rewrite.go
+++ b/tool/rewrite/rewrite.go
@@ -24,7 +24,7 @@ import (
 	"regexp"
 	"strings"
 
-	"github.com/jsonnet-bundler/jsonnet-bundler/spec/deps"
+	"github.com/jsonnet-bundler/jsonnet-bundler/spec/v1/deps"
 )
 
 var expr = regexp.MustCompile(`(?mU)(import ["'])(.*)(\/.*["'])`)
diff --git a/tool/rewrite/rewrite_test.go b/tool/rewrite/rewrite_test.go
index 67721f8..6cd9549 100644
--- a/tool/rewrite/rewrite_test.go
+++ b/tool/rewrite/rewrite_test.go
@@ -22,7 +22,7 @@ import (
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 
-	"github.com/jsonnet-bundler/jsonnet-bundler/spec/deps"
+	"github.com/jsonnet-bundler/jsonnet-bundler/spec/v1/deps"
 )
 
 const sample = `