diff --git a/indra/newview/llfloaterimsessiontab.cpp b/indra/newview/llfloaterimsessiontab.cpp
index d43381041b4cfc9c633a31da9c4174c78baaf097..08c2b951df0fe1adc4d92226c132bb3238e4511d 100644
--- a/indra/newview/llfloaterimsessiontab.cpp
+++ b/indra/newview/llfloaterimsessiontab.cpp
@@ -691,8 +691,13 @@ void LLFloaterIMSessionTab::processChatHistoryStyleUpdate()
 
 void LLFloaterIMSessionTab::updateCallBtnState(bool callIsActive)
 {
-	getChild<LLButton>("voice_call_btn")->setImageOverlay(
+	LLButton* voiceButton = getChild<LLButton>("voice_call_btn");
+	voiceButton->setImageOverlay(
 			callIsActive? getString("call_btn_stop") : getString("call_btn_start"));
+
+	voiceButton->setToolTip(
+			callIsActive? getString("end_call_button_tooltip") : getString("start_call_button_tooltip"));
+
     enableDisableCallBtn();
 
 }
diff --git a/indra/newview/skins/default/xui/en/floater_im_session.xml b/indra/newview/skins/default/xui/en/floater_im_session.xml
index 1d74f1bc259dea3df7d27c465c7568d9d3f6d550..faf54774f65fee45b0c57362ad9b179e022a6c72 100644
--- a/indra/newview/skins/default/xui/en/floater_im_session.xml
+++ b/indra/newview/skins/default/xui/en/floater_im_session.xml
@@ -43,6 +43,12 @@
      <floater.string
      name="tooltip_to_main_window"
      value="Move this conversation back to main window"/>
+  <floater.string
+     name="start_call_button_tooltip"
+     value="Open voice connection"/>
+  <floater.string
+     name="end_call_button_tooltip"
+     value="Close voice connection"/>
     <view
         follows="all"
         layout="topleft"