diff --git a/djangorestframework/permissions.py b/djangorestframework/permissions.py
index c10569d4d..945023cec 100644
--- a/djangorestframework/permissions.py
+++ b/djangorestframework/permissions.py
@@ -109,7 +109,7 @@ class BaseThrottle(BasePermission):
     def get_cache_key(self):
         """
         Should return a unique cache-key which can be used for throttling.
-        Muse be overridden.
+        Must be overridden.
         """
         pass