diff --git a/src/vim9expr.c b/src/vim9expr.c
index b765448..58ff395 100644
--- a/src/vim9expr.c
+++ b/src/vim9expr.c
@@ -796,7 +796,7 @@
 	int	    outer_loop_depth = -1;
 	int	    outer_loop_idx = -1;
 
-	name = vim_strnsave(*arg, end - *arg);
+	name = vim_strnsave(*arg, len);
 	if (name == NULL)
 	    return FAIL;