diff --git a/Lib/fontTools/misc/classifyTools.py b/Lib/fontTools/misc/classifyTools.py
index 0718c88ff..ab3b8681e 100644
--- a/Lib/fontTools/misc/classifyTools.py
+++ b/Lib/fontTools/misc/classifyTools.py
@@ -23,7 +23,7 @@ class Classifier:
 		Add a set to the classifier.  Any iterable is accepted.
 		"""
 		if not set_of_things:
-			return;
+			return
 
 		self._dirty = True