diff --git a/classes/Profile.php b/classes/Profile.php
index f0a326e212..7005e776a5 100644
--- a/classes/Profile.php
+++ b/classes/Profile.php
@@ -595,7 +595,7 @@ class Profile extends Managed_DataObject
             if (Event::handle('StartJoinGroup', array($group, $this))) {
                 $join = Group_member::join($group->id, $this->id);
                 self::blow('profile:groups:%d', $this->id);
-                self::blow('group:members:%d', $group->id);
+                self::blow('group:member_ids:%d', $group->id);
                 self::blow('group:member_count:%d', $group->id);
                 Event::handle('EndJoinGroup', array($group, $this));
             }
@@ -617,7 +617,7 @@ class Profile extends Managed_DataObject
         if (Event::handle('StartLeaveGroup', array($group, $this))) {
             Group_member::leave($group->id, $this->id);
             self::blow('profile:groups:%d', $this->id);
-            self::blow('group:members:%d', $group->id);
+            self::blow('group:member_ids:%d', $group->id);
             self::blow('group:member_count:%d', $group->id);
             Event::handle('EndLeaveGroup', array($group, $this));
         }
diff --git a/classes/User_group.php b/classes/User_group.php
index f99feeb874..406537dd8a 100644
--- a/classes/User_group.php
+++ b/classes/User_group.php
@@ -148,7 +148,7 @@ class User_group extends Managed_DataObject
             $ids = $this->getMemberIDs($offset,
                                        $limit);
         } else {
-            $key = sprintf('group:members:%d', $this->id);
+            $key = sprintf('group:member_ids:%d', $this->id);
             $window = self::cacheGet($key);
             if ($window === false) {
                 $window = $this->getMemberIDs(0,