diff --git a/src/vim9cmds.c b/src/vim9cmds.c
index 06964d5..ecf31dc 100644
--- a/src/vim9cmds.c
+++ b/src/vim9cmds.c
@@ -2531,7 +2531,8 @@
     char_u	*p = arg;
     type_T	*stack_type;
 
-    if (*p != NUL && *p != '|' && *p != '\n')
+    if (*p != NUL && *p != '|' && *p != '\n'
+					&& (legacy || !vim9_comment_start(p)))
     {
 	// For a lambda, "return expr" is always used, also when "expr" results
 	// in a void.