diff --git a/ext/session/session.c b/ext/session/session.c
index 277a84e88ba..b1565672593 100644
--- a/ext/session/session.c
+++ b/ext/session/session.c
@@ -732,7 +732,7 @@ static int migrate_global(HashTable *ht, HashPosition *pos TSRMLS_DC)
 			break;
 		case HASH_KEY_IS_LONG:
 			php_error_docref(NULL TSRMLS_CC, E_NOTICE, "The session bug compatibility code will not "
-					"try to locate the global variable $%d due to its "
+					"try to locate the global variable $%lu due to its "
 					"numeric nature.", num_key);
 			break;
 	}