diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
index 29404c3..1c083b2 100644
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -1216,7 +1216,7 @@
     }
     unicode_aswidechar(unicode, buffer, buflen);
     if (size)
-        *size = buflen;
+        *size = buflen - 1;
     return buffer;
 }