diff --git a/Modules/datetimemodule.c b/Modules/datetimemodule.c
index f3103ea..5401068 100644
--- a/Modules/datetimemodule.c
+++ b/Modules/datetimemodule.c
@@ -2565,6 +2565,7 @@
     register unsigned char *p;
     register long x;
 
+    assert(_Py_HashSecret_Initialized);
     p = (unsigned char *) data;
     x = _Py_HashSecret.prefix;
     x ^= *p << 7;