diff --git a/bin/mechanicaldiff.py b/bin/mechanicaldiff.py
index 4a8ed1f..cd11731 100755
--- a/bin/mechanicaldiff.py
+++ b/bin/mechanicaldiff.py
@@ -1,5 +1,6 @@
 #!/usr/bin/env python3
 
+import re
 import sys
 
 
@@ -18,7 +19,8 @@ def should_include_change(change_lines: list[str], search: str, replace: str) ->
             added_lines.append(line[1:])
             continue
         raise ValueError("Unexpected non-change line in change block.")
-    return True
+    transformed_removed = [re.sub(search, replace, line) for line in removed_lines]
+    return transformed_removed == added_lines
 
 
 def should_include_hunk(hunk_text: str, search: str, replace: str) -> bool: