diff --git a/indra/llui/llchatmentionhelper.cpp b/indra/llui/llchatmentionhelper.cpp
index 5745389a58..d7cf60daef 100644
--- a/indra/llui/llchatmentionhelper.cpp
+++ b/indra/llui/llchatmentionhelper.cpp
@@ -39,6 +39,13 @@ bool LLChatMentionHelper::isActive(const LLUICtrl* ctrl) const
 
 bool LLChatMentionHelper::isCursorInNameMention(const LLWString& wtext, S32 cursor_pos, S32* mention_start_pos) const
 {
+    // <FS:PP> Enable auto-completion of @ mentions
+    static LLUICachedControl<bool> useMentionAutoComplete("FSUseChatMentionAutoComplete", true);
+    if (!useMentionAutoComplete)
+    {
+        return false;
+    }
+    // </FS:PP>
     if (cursor_pos <= 0 || cursor_pos > static_cast<S32>(wtext.size()))
         return false;
 
diff --git a/indra/llui/llemojihelper.cpp b/indra/llui/llemojihelper.cpp
index 7d5be5f049..3367eb0f0a 100644
--- a/indra/llui/llemojihelper.cpp
+++ b/indra/llui/llemojihelper.cpp
@@ -58,7 +58,7 @@ bool LLEmojiHelper::isActive(const LLUICtrl* ctrl_p) const
 bool LLEmojiHelper::isCursorInEmojiCode(const LLWString& wtext, S32 cursorPos, S32* pShortCodePos)
 {
     // <FS:PP> FIRE-33735: Option to suppress emoji chooser window from automatically popping up while typing in chat bars
-    static LLUICachedControl<bool> FSEnableEmojiWindowPopupWhileTyping("FSEnableEmojiWindowPopupWhileTyping");
+    static LLUICachedControl<bool> FSEnableEmojiWindowPopupWhileTyping("FSEnableEmojiWindowPopupWhileTyping", true);
     if (!FSEnableEmojiWindowPopupWhileTyping)
     {
         return false;
diff --git a/indra/newview/app_settings/settings.xml b/indra/newview/app_settings/settings.xml
index 407b57c184..73effa26aa 100644
--- a/indra/newview/app_settings/settings.xml
+++ b/indra/newview/app_settings/settings.xml
@@ -26469,6 +26469,17 @@ Change of this parameter will affect the layout of buttons in notification toast
       <key>Value</key>
       <integer>1</integer>
     </map>
+    <key>FSUseChatMentionAutoComplete</key>
+    <map>
+      <key>Comment</key>
+      <string>Enable auto-completion when typing @ mentions in chat.</string>
+      <key>Persist</key>
+      <integer>1</integer>
+      <key>Type</key>
+      <string>Boolean</string>
+      <key>Value</key>
+      <integer>1</integer>
+    </map>
     <key>FSUseBWEmojis</key>
     <map>
       <key>Comment</key>
diff --git a/indra/newview/skins/default/xui/en/panel_preferences_chat.xml b/indra/newview/skins/default/xui/en/panel_preferences_chat.xml
index 27137d2c16..2e88b99ba4 100644
--- a/indra/newview/skins/default/xui/en/panel_preferences_chat.xml
+++ b/indra/newview/skins/default/xui/en/panel_preferences_chat.xml
@@ -916,6 +916,14 @@
 		 top_pad="1"
 		 height="16"
 		 width="400" />
+		<check_box
+		 layout="topleft"
+		 top_pad="1"
+		 height="16"
+		 width="400"
+		 control_name="FSUseChatMentionAutoComplete"
+		 name="FSUseChatMentionAutoComplete"
+		 label="Enable automatic @ mentions window while typing in chat bars"/>
 		<check_box
 		 layout="topleft"
 		 top_pad="1"
diff --git a/indra/newview/skins/default/xui/pl/panel_preferences_chat.xml b/indra/newview/skins/default/xui/pl/panel_preferences_chat.xml
index 1b5493a17e..8e40f7e16f 100644
--- a/indra/newview/skins/default/xui/pl/panel_preferences_chat.xml
+++ b/indra/newview/skins/default/xui/pl/panel_preferences_chat.xml
@@ -142,6 +142,7 @@
 			<check_box label="Włącz automatyczne odgadywanie imion w pasku czatu w pobliżu" name="FSChatbarNamePrediction"/>
 			<check_box name="AllowMUpose" label="&quot;:&quot; synonimem dla &quot;/me&quot;"/>
 			<check_box name="AutoCloseOOC" label="Domykaj ((nawiasy)) dla czatu OOC"/>
+			<check_box name="FSUseChatMentionAutoComplete" label="Automatyczne wyświetlanie okna wzmianek @ podczas pisania w paskach czatu"/>
 			<check_box name="FSEnableEmojiWindowPopupWhileTyping" label="Automatyczne wyświetlanie okna wyboru emoji podczas pisania w paskach czatu"/>
 			<check_box name="FSShowEmojiButton" label="Przycisk emoji w pasku czatu dla sesji IM i czatu w pobliżu"/>
 			<check_box name="FSShowIMSendButton" label="Przycisk wysyłania wiadomości w pasku czatu dla sesji IM"/>