diff --git a/tools/gn/misc/vim/gn-format.py b/tools/gn/misc/vim/gn-format.py
index 561c76c..7e5d6a4 100644
--- a/tools/gn/misc/vim/gn-format.py
+++ b/tools/gn/misc/vim/gn-format.py
@@ -53,7 +53,7 @@
       lines = lines[:-1]
     sequence = difflib.SequenceMatcher(None, vim.current.buffer, lines)
     for op in reversed(sequence.get_opcodes()):
-      if op[0] is not 'equal':
+      if op[0] != 'equal':
         vim.current.buffer[op[1]:op[2]] = lines[op[3]:op[4]]
 
 main()