diff --git a/src/vim9cmds.c b/src/vim9cmds.c
index 92605cf..392bab4 100644
--- a/src/vim9cmds.c
+++ b/src/vim9cmds.c
@@ -2661,6 +2661,8 @@
 	    // for an inline function without a specified return type.  Set the
 	    // return type here.
 	    stack_type = get_type_on_stack(cctx, 0);
+	    if (check_type_is_value(stack_type) == FAIL)
+		return NULL;
 	    if ((check_return_type && (cctx->ctx_ufunc->uf_ret_type == NULL
 				|| cctx->ctx_ufunc->uf_ret_type == &t_unknown))
 		    || (!check_return_type