diff --git a/indra/newview/llcallingcard.cpp b/indra/newview/llcallingcard.cpp
index acf45de69e..e3b9f687b0 100644
--- a/indra/newview/llcallingcard.cpp
+++ b/indra/newview/llcallingcard.cpp
@@ -540,13 +540,20 @@ void LLAvatarTracker::notifyParticularFriendObservers(const LLUUID& buddy_id)
         return;
 
     // Notify observers interested in buddy_id.
-    observer_set_t& obs = obs_it->second;
+	
+	// <FS:ND> FIRE-6077; FIRE-6227; FIRE-6431; SUP-9654; make a copy of observer_set. Just in case some implementation of changed() calls add/remove...Observer
+	
+	//    observer_set_t& obs = obs_it->second;
+    observer_set_t obs = obs_it->second;
+
+	// </FS:ND:
+
     for (observer_set_t::iterator ob_it = obs.begin(); ob_it != obs.end(); ob_it++)
     {
-		if (*ob_it)
-			(*ob_it)->changed(mModifyMask);
-		else
-			llwarns << "Invalid observer" << llendl;
+		(*ob_it)->changed(mModifyMask);
+
+		// <FS:ND/> Paranoia check. Of course someone could add x observer than add the same amount of x. That won't be found by comparing size alone, but it is good enough for a quick test 
+		llassert( obs.size() == obs_it->second.size() );
     }
 }
 
@@ -583,10 +590,20 @@ void LLAvatarTracker::notifyFriendPermissionObservers(const LLUUID& buddy_id)
 		return;
 	}
     // Notify observers interested in buddy_id.
-    observer_set_t& obs = obs_it->second;
+
+	// <FS:ND> FIRE-6077; FIRE-6227; FIRE-6431; SUP-9654; make a copy of observer_set. Just in case some implementation of changed() calls add/remove...Observer
+
+	//    observer_set_t& obs = obs_it->second;
+    observer_set_t obs = obs_it->second;
+
+	// </FS:ND>
+
     for (observer_set_t::iterator ob_it = obs.begin(); ob_it != obs.end(); ob_it++)
     {
 		(*ob_it)->changed(LLFriendObserver::PERMS);
+		
+		// <FS:ND/> Paranoia check. Of course someone could add x observer than add the same amount of x. That won't be found by comparing size alone, but it is good enough for a quick test 
+		llassert( obs.size() == obs_it->second.size() );
     }
 }