diff --git a/Modules/_cryptmodule.c b/Modules/_cryptmodule.c
index 5d03f45..00c1f4f 100644
--- a/Modules/_cryptmodule.c
+++ b/Modules/_cryptmodule.c
@@ -42,6 +42,9 @@
 #else
     crypt_result = crypt(word, salt);
 #endif
+    if (crypt_result == NULL) {
+        return PyErr_SetFromErrno(PyExc_OSError);
+    }
     return Py_BuildValue("s", crypt_result);
 }