#13406: silence deprecation warnings in test_codecs.
diff --git a/Modules/_codecsmodule.c b/Modules/_codecsmodule.c
index 58ffc1d..4cd5c23 100644
--- a/Modules/_codecsmodule.c
+++ b/Modules/_codecsmodule.c
@@ -688,7 +688,7 @@
             return NULL;
 
         if (PyErr_WarnEx(PyExc_DeprecationWarning,
-                         "unicode_internal codecs has been deprecated",
+                         "unicode_internal codec has been deprecated",
                          1))
             return NULL;