diff --git a/src/pycalver/rewrite.py b/src/pycalver/rewrite.py
index 78ca821..a9bb7fa 100644
--- a/src/pycalver/rewrite.py
+++ b/src/pycalver/rewrite.py
@@ -148,7 +148,7 @@ def diff(new_version: str, file_patterns: config.PatternsByFilePath) -> str:
 
     full_diff = ""
     file_path: str
-    for file_path, patterns in file_patterns.items():
+    for file_path, patterns in sorted(file_patterns.items()):
         with io.open(file_path, mode="rt", encoding="utf-8") as fh:
             content = fh.read()