diff --git a/src/vim9class.c b/src/vim9class.c
index 4d0b4e8..5d68459 100644
--- a/src/vim9class.c
+++ b/src/vim9class.c
@@ -3855,6 +3855,8 @@
 
     if (o1 == o2)
 	return TRUE;
+    if (o1 == NULL || o2 == NULL)
+	return FALSE;
 
     cl1 = o1->obj_class;
     cl2 = o2->obj_class;