diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
index d46ab2a..35c8a24 100644
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -9356,6 +9356,7 @@
     PyObject *thousands_sep,
     Py_UCS4 *maxchar)
 {
+    min_width = Py_MAX(0, min_width);
     if (writer) {
         assert(digits != NULL);
         assert(maxchar == NULL);
@@ -9366,7 +9367,6 @@
     }
     assert(0 <= d_pos);
     assert(0 <= n_digits);
-    assert(0 <= min_width);
     assert(grouping != NULL);
 
     if (digits != NULL) {