diff --git a/orangecanvas/application/canvasmain.py b/orangecanvas/application/canvasmain.py
index 1dd1fbe12..3c6b05229 100644
--- a/orangecanvas/application/canvasmain.py
+++ b/orangecanvas/application/canvasmain.py
@@ -2737,7 +2737,7 @@ def collectall(
                                      IncompatibleChannelTypeError))
     )
     contents = []
-    if missing_node_defs is not None:
+    if missing_node_defs:
         contents.extend([
             "Missing node definitions:",
             *["  \N{BULLET} " + e.args[0] for e in missing_node_defs],