diff --git a/indra/llui/llnotifications.cpp b/indra/llui/llnotifications.cpp
index 17c8c32ee3..a115c6abb8 100644
--- a/indra/llui/llnotifications.cpp
+++ b/indra/llui/llnotifications.cpp
@@ -1936,6 +1936,7 @@ void LLPostponedNotification::lookupName(const LLUUID& id,
 	}
 	else
 	{
+		mFromId = id; // <FS:Ansariel> FIRE-29943: Item shared messaged logging to wrong IM logfile if user is offline
 		fetchAvatarName(id);
 	}
 }
diff --git a/indra/llui/llnotifications.h b/indra/llui/llnotifications.h
index 1a6b320a4c..aedf5c8dcf 100644
--- a/indra/llui/llnotifications.h
+++ b/indra/llui/llnotifications.h
@@ -1043,7 +1043,8 @@ protected:
 	LLPostponedNotification()
 		: mParams(),
 		mName(),
-		mAvatarNameCacheConnection()
+		mAvatarNameCacheConnection(),
+		mFromId(LLUUID::null) // <FS:Ansariel> FIRE-29943: Item shared messaged logging to wrong IM logfile if user is offline
 	{}
 
 	virtual ~LLPostponedNotification()
@@ -1064,6 +1065,7 @@ protected:
 	LLNotification::Params mParams;
 	std::string mName;
 	boost::signals2::connection mAvatarNameCacheConnection;
+	LLUUID mFromId; // <FS:Ansariel> FIRE-29943: Item shared messaged logging to wrong IM logfile if user is offline
 };
 
 // Stores only persistent notifications.
diff --git a/indra/newview/llimprocessing.cpp b/indra/newview/llimprocessing.cpp
index 57c5ea688f..0e3183f5a6 100644
--- a/indra/newview/llimprocessing.cpp
+++ b/indra/newview/llimprocessing.cpp
@@ -183,7 +183,22 @@ protected:
     void modifyNotificationParams()
     {
         LLSD payload = mParams.payload;
-        payload["SESSION_NAME"] = mName;
+        // <FS:Ansariel> FIRE-29943: Item shared messaged logging to wrong IM logfile if user is offline
+        //payload["SESSION_NAME"] = mName;
+        LLAvatarName av_name;
+        // This should work since modifyNotificationParams() is invoked after we already
+        // retrieved the avatar name
+        if (mFromId.notNull() && LLAvatarNameCache::instance().getName(mFromId, &av_name))
+        {
+            // LLHandlerUtil::logToIM() will transform this into the correct filename
+            payload["SESSION_NAME"] = av_name.getLegacyName();
+        }
+        else
+        {
+            payload["SESSION_NAME"] = mName;
+        }
+        // </FS:Ansariel>
+
         mParams.payload = payload;
     }
 };