diff --git a/.gitignore b/.gitignore
index c899f50..e910e29 100644
--- a/.gitignore
+++ b/.gitignore
@@ -216,4 +216,7 @@ fabric.properties
 .idea/httpRequests
 
 # Android studio 3.1+ serialized cache file
-.idea/caches/build_file_checksums.ser
\ No newline at end of file
+.idea/caches/build_file_checksums.ser
+
+# Visual Studio Code
+.vscode
diff --git a/src/bumpver/v2version.py b/src/bumpver/v2version.py
index 39e0e1e..8cd1ec7 100644
--- a/src/bumpver/v2version.py
+++ b/src/bumpver/v2version.py
@@ -754,6 +754,11 @@ def incr(
     else:
         cur_vinfo = old_vinfo._replace(**cur_cinfo._asdict())
 
+    has_tag_part = cur_vinfo.tag != "final"
+    if tag_num and not tag and not has_tag_part:
+        logger.error("Invalid arguments, non-final --tag=<tag> is needed to use --tag-num.")
+        return None
+
     cur_vinfo = _incr_numeric(
         raw_pattern,
         old_vinfo,
diff --git a/test/test_version.py b/test/test_version.py
index 191a534..40b3da1 100644
--- a/test/test_version.py
+++ b/test/test_version.py
@@ -73,6 +73,18 @@ def test_bump_random(monkeypatch):
         cur_version = new_version
 
 
+def test_bump_tag_num():
+    raw_pattern = "MAJOR.MINOR.PATCH[PYTAGNUM]"
+    cur_version = "0.1.1b0"
+    assert v2version.incr(cur_version, raw_pattern, tag_num=True) == "0.1.1b1"
+
+
+def test_bump_tag_num_without_tag():
+    raw_pattern = "MAJOR.MINOR.PATCH[PYTAGNUM]"
+    cur_version = "0.1.1"
+    assert v2version.incr(cur_version, raw_pattern, tag_num=True) is None
+
+
 def test_parse_version_info():
     version_str  = "v201712.0001-alpha"
     version_info = v1version.parse_version_info(version_str)