diff --git a/plover/oslayer/osx/keyboardcontrol.py b/plover/oslayer/osx/keyboardcontrol.py
index f230ffb92..17ff61400 100644
--- a/plover/oslayer/osx/keyboardcontrol.py
+++ b/plover/oslayer/osx/keyboardcontrol.py
@@ -330,7 +330,7 @@ def send_string(self, string):
         # and add the sequence to the key plan when called as a function.
         def apply_raw():
             if hasattr(apply_raw, 'sequence') \
-                    and len(apply_raw.sequence) is not 0:
+                    and len(apply_raw.sequence) != 0:
                 apply_raw.sequence.extend(apply_raw.release_modifiers)
                 key_plan.append((self.RAW_PRESS, apply_raw.sequence))
             apply_raw.sequence = []