diff --git a/src/vat/api_format.c b/src/vat/api_format.c
index 45ba025..48c1cca 100644
--- a/src/vat/api_format.c
+++ b/src/vat/api_format.c
@@ -2151,7 +2151,7 @@
     }
 
   /* It's fairly hard to get "../oopsie" through unformat; just in case */
-  if (strstr (file, "..") || index (file, '/'))
+  if (strstr (file, "..") || strchr (file, '/'))
     {
       errmsg ("illegal characters in filename '%s'", file);
       return 0;