diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
index bcd5b64..5a2b708 100644
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -401,7 +401,7 @@
                 else
                     printf("U+%04x", ch);
             }
-            printf("} (len=%u)\n", ascii->length);
+            printf("} (len=%lu)\n", ascii->length);
             abort();
         }
         if (kind == PyUnicode_1BYTE_KIND) {