diff --git a/Modules/rotormodule.c b/Modules/rotormodule.c
index dcca0c6..6759244 100644
--- a/Modules/rotormodule.c
+++ b/Modules/rotormodule.c
@@ -620,4 +620,8 @@
 {
 	Rotor_Type.ob_type = &PyType_Type;
 	(void)Py_InitModule("rotor", rotor_methods);
+	if (PyErr_Warn(PyExc_DeprecationWarning,
+		       "the rotor module uses an insecure algorithm "
+                       "and is deprecated") < 0)
+		return;
 }