diff --git a/src/vim9expr.c b/src/vim9expr.c
index b8458aa..d600cb0 100644
--- a/src/vim9expr.c
+++ b/src/vim9expr.c
@@ -293,6 +293,13 @@
 	}
     }
 
+    if (cl == NULL)
+    {
+	// TODO: this should not give an error but be handled at runtime
+	emsg(_(e_incomplete_type));
+	return FAIL;
+    }
+
     ++*arg;
     char_u *name = *arg;
     char_u *name_end = find_name_end(name, NULL, NULL, FNE_CHECK_START);