diff --git a/lib/url.c b/lib/url.c
index 9ae977e11bdc03aa2e31e9d9f77c5f2356047563..a290e3cea2c93d0402a632db91fe9967185d064b 100644
--- a/lib/url.c
+++ b/lib/url.c
@@ -1115,7 +1115,7 @@ CURLcode Curl_setopt(struct SessionHandle *data, CURLoption option,
      * CURL_REDIR_POST_ALL - POST is kept as POST after 301, 302 and 303
      * other - POST is kept as POST after 301 and 302
      */
-    long postRedir = va_arg(param, long);
+    int postRedir = curlx_sltosi(va_arg(param, long));
     data->set.keep_post = postRedir & CURL_REDIR_POST_ALL;
   }
   break;