diff --git a/Modules/pyexpat.c b/Modules/pyexpat.c
index 21ab088..ae98ef7 100644
--- a/Modules/pyexpat.c
+++ b/Modules/pyexpat.c
@@ -831,7 +831,7 @@
     if (len > buf_size) {
         PyErr_Format(PyExc_ValueError,
                      "read() returned too much data: "
-                     "%i bytes requested, %zi returned",
+                     "%i bytes requested, %zd returned",
                      buf_size, len);
         goto finally;
     }