diff --git a/contrib/examples/httpd/post_example/post_example.c b/contrib/examples/httpd/post_example/post_example.c
index 2debe29d..975a7f6e 100644
--- a/contrib/examples/httpd/post_example/post_example.c
+++ b/contrib/examples/httpd/post_example/post_example.c
@@ -93,7 +93,7 @@ httpd_post_receive_data(void *connection, struct pbuf *p)
 {
   err_t ret;
 
-  LWIP_ASSERT("NULL pbuf", p = NULL);
+  LWIP_ASSERT("NULL pbuf", p != NULL);
 
   if (current_connection == connection) {
     u16_t token_user = pbuf_memfind(p, "user=", 5, 0);