diff --git a/Python/ast.c b/Python/ast.c
index 4ae9d75..d2f063b 100644
--- a/Python/ast.c
+++ b/Python/ast.c
@@ -3395,6 +3395,7 @@
                 goto onError;
             if (*bytesmode != subbm) {
                 ast_error(n, "cannot mix bytes and nonbytes literals");
+                Py_DECREF(s);
                 goto onError;
             }
             if (PyBytes_Check(v) && PyBytes_Check(s)) {