diff --git a/PowerEditor/src/Notepad_plus.cpp b/PowerEditor/src/Notepad_plus.cpp
index 62a938275..98e862146 100644
--- a/PowerEditor/src/Notepad_plus.cpp
+++ b/PowerEditor/src/Notepad_plus.cpp
@@ -6702,14 +6702,6 @@ void Notepad_plus::notifyBufferChanged(Buffer * buffer, int mask)
 		return;
 	}
 
-	if (mask & (BufferChangeLanguage))
-	{
-		if (mainActive)
-			_autoCompleteMain.setLanguage(buffer->getLangType());
-		if (subActive)
-			_autoCompleteSub.setLanguage(buffer->getLangType());
-	}
-
 	if ((currentView() == MAIN_VIEW) && !mainActive)
 		return;
 
@@ -6732,9 +6724,9 @@ void Notepad_plus::notifyBufferChanged(Buffer * buffer, int mask)
 	{
 		checkLangsMenu(-1);	//let Notepad++ do search for the item
 		setLangStatus(buffer->getLangType());
-		if (_mainEditView.getCurrentBuffer() == buffer)
+		if (mainActive)
 			_autoCompleteMain.setLanguage(buffer->getLangType());
-		else if (_subEditView.getCurrentBuffer() == buffer)
+		else if (subActive)
 			_autoCompleteSub.setLanguage(buffer->getLangType());
 
 		if (_pFuncList && (!_pFuncList->isClosed()) && _pFuncList->isVisible())
diff --git a/PowerEditor/src/NppBigSwitch.cpp b/PowerEditor/src/NppBigSwitch.cpp
index 01c988afc..19b26bda2 100644
--- a/PowerEditor/src/NppBigSwitch.cpp
+++ b/PowerEditor/src/NppBigSwitch.cpp
@@ -4135,6 +4135,15 @@ LRESULT Notepad_plus::process(HWND hwnd, UINT message, WPARAM wParam, LPARAM lPa
 			return TRUE;
 		}
 
+		case NPPM_INTERNAL_RELOADFUNCTIONLIST:
+		{
+			if (_pFuncList && (!_pFuncList->isClosed()) && _pFuncList->isVisible())
+			{
+				_pFuncList->reload();
+			}
+			return TRUE;
+		}
+
 		default:
 		{
 			if (message == WDN_NOTIFY)
diff --git a/PowerEditor/src/ScintillaComponent/ScintillaEditView.cpp b/PowerEditor/src/ScintillaComponent/ScintillaEditView.cpp
index a8abc5eb7..98f7d61d6 100644
--- a/PowerEditor/src/ScintillaComponent/ScintillaEditView.cpp
+++ b/PowerEditor/src/ScintillaComponent/ScintillaEditView.cpp
@@ -1723,6 +1723,10 @@ void ScintillaEditView::setLanguage(LangType langType)
 
 	if (_currentBuffer->getLastLangType() > 0 && !_currentBuffer->isUntitled())
 	{
+		// To improve switching lexer performance, here's the tip:
+		// 1. Set current document to a blank document
+		// 2. Set a new lexer
+		// 3. Reset back to the current document
 		saveCurrentPos();
 		Document prev = execute(SCI_GETDOCPOINTER);
 		execute(SCI_SETMODEVENTMASK, MODEVENTMASK_OFF);
@@ -1738,6 +1742,11 @@ void ScintillaEditView::setLanguage(LangType langType)
 		maintainStateForNpc();
 		setCRLF();
 		restoreCurrentPosPreStep();
+
+		// When buffer sets lang type ("_currentBuffer->setLangType(langType);"), it'll call doNotify(BufferChangeLanguage | BufferChangeLexing),
+		// then FunctionList will be reloaded. However, it'll be reloaded on the blank document.
+		// That's why here we do again FunctionList reload, after the current document be reset back.
+		::SendMessage(_hParent, NPPM_INTERNAL_RELOADFUNCTIONLIST, 0, 0);
 	}
 	else
 	{
diff --git a/PowerEditor/src/resource.h b/PowerEditor/src/resource.h
index 1117177a4..8f0d69054 100644
--- a/PowerEditor/src/resource.h
+++ b/PowerEditor/src/resource.h
@@ -745,6 +745,7 @@
 	#define NPPM_INTERNAL_LWINDENT                      (NOTEPADPLUS_USER_INTERNAL + 105)
 	#define NPPM_INTERNAL_CHECKDOCSTATUS                (NOTEPADPLUS_USER_INTERNAL + 106)
 	#define NPPM_INTERNAL_HIDEMENURIGHTSHORTCUTS        (NOTEPADPLUS_USER_INTERNAL + 107)
+	#define NPPM_INTERNAL_RELOADFUNCTIONLIST            (NOTEPADPLUS_USER_INTERNAL + 108)