diff --git a/src/mod/endpoints/mod_verto/mod_verto.c b/src/mod/endpoints/mod_verto/mod_verto.c
index b63a9243c3..0bf914df8c 100644
--- a/src/mod/endpoints/mod_verto/mod_verto.c
+++ b/src/mod/endpoints/mod_verto/mod_verto.c
@@ -1237,7 +1237,7 @@ static void client_run(jsock_t *jsock)
 			bytes = ws_read_frame(&jsock->ws, &oc, &data);
 	
 			if (bytes < 0) {
-				die("BAD READ %ld\n", bytes);
+				die("BAD READ %" SWITCH_SIZE_T_FMT "\n", bytes);
 				break;
 			}