diff --git a/dix/devices.c b/dix/devices.c
index c2d4f22a5..7d8fd0398 100644
--- a/dix/devices.c
+++ b/dix/devices.c
@@ -1241,6 +1241,7 @@ DoSetModifierMapping(ClientPtr client, KeyCode *inputMap,
             }
             else {
                 pDev->key->modifierKeyMap = NULL;
+                pDev->key->maxKeysPerModifier = 0;
             }
         }
     }