diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
index bb1c083..2f30877 100644
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -6136,7 +6136,7 @@
     if (first_invalid_escape != NULL) {
         if (PyErr_WarnFormat(PyExc_DeprecationWarning, 1,
                              "invalid escape sequence '\\%c'",
-                             *first_invalid_escape) < 0) {
+                             (unsigned char)*first_invalid_escape) < 0) {
             Py_DECREF(result);
             return NULL;
         }