diff --git a/Python/_warnings.c b/Python/_warnings.c
index 956b3f5..c84bd85 100644
--- a/Python/_warnings.c
+++ b/Python/_warnings.c
@@ -498,7 +498,7 @@
                 }
                 else if (!is_true) {
                     Py_DECREF(*filename);
-                    *filename = PyString_FromString("__main__");
+                    *filename = PyUnicode_FromString("__main__");
                     if (*filename == NULL)
                         goto handle_error;
                 }