diff --git a/PowerEditor/src/MISC/PluginsManager/Notepad_plus_msgs.h b/PowerEditor/src/MISC/PluginsManager/Notepad_plus_msgs.h
index fb0c2b5b4..a41b50779 100644
--- a/PowerEditor/src/MISC/PluginsManager/Notepad_plus_msgs.h
+++ b/PowerEditor/src/MISC/PluginsManager/Notepad_plus_msgs.h
@@ -746,3 +746,8 @@ enum Platform { PF_UNKNOWN, PF_X86, PF_X64, PF_IA64, PF_ARM64 };
 	//scnNotification->nmhdr.code = NPPN_CMDLINEPLUGINMSG;
 	//scnNotification->nmhdr.hwndFrom = hwndNpp;
 	//scnNotification->nmhdr.idFrom = pluginMessage; //where pluginMessage is pointer of type wchar_t
+
+	#define NPPN_EXTERNALLEXERBUFFER (NPPN_FIRST + 29)  // To notify lexer plugins that the buffer (in idFrom) is just applied to a external lexer
+	//scnNotification->nmhdr.code = NPPN_EXTERNALLEXERBUFFER;
+	//scnNotification->nmhdr.hwndFrom = hwndNpp;
+	//scnNotification->nmhdr.idFrom = BufferID; //where pluginMessage is pointer of type wchar_t
diff --git a/PowerEditor/src/NppBigSwitch.cpp b/PowerEditor/src/NppBigSwitch.cpp
index 246920312..6380c4204 100644
--- a/PowerEditor/src/NppBigSwitch.cpp
+++ b/PowerEditor/src/NppBigSwitch.cpp
@@ -2132,6 +2132,18 @@ LRESULT Notepad_plus::process(HWND hwnd, UINT message, WPARAM wParam, LPARAM lPa
 			return TRUE;
 		}
 
+		case NPPM_INTERNAL_EXTERNALLEXERBUFFER:
+		{
+			// A buffer is just applied to an external lexer, let's send a notification to lexer plugin 
+			// so the concerning plugin can manage it (associate the buffer & lexer instance).
+			SCNotification scnN{};
+			scnN.nmhdr.code = NPPN_EXTERNALLEXERBUFFER;
+			scnN.nmhdr.hwndFrom = hwnd;
+			scnN.nmhdr.idFrom = lParam;
+			_pluginsManager.notify(&scnN);
+			return TRUE;
+		}
+
 		case WM_QUERYENDSESSION:
 		{
 			// app should return TRUE or FALSE immediately upon receiving this message,
diff --git a/PowerEditor/src/ScintillaComponent/ScintillaEditView.cpp b/PowerEditor/src/ScintillaComponent/ScintillaEditView.cpp
index c7e66c7ec..32bc02776 100644
--- a/PowerEditor/src/ScintillaComponent/ScintillaEditView.cpp
+++ b/PowerEditor/src/ScintillaComponent/ScintillaEditView.cpp
@@ -902,6 +902,8 @@ void ScintillaEditView::setExternalLexer(LangType typeDoc)
 		return;
 	execute(SCI_SETILEXER, 0, reinterpret_cast<LPARAM>(iLex5));
 
+	::SendMessage(_hParent, NPPM_INTERNAL_EXTERNALLEXERBUFFER, 0, (LPARAM)getCurrentBufferID());
+
 	WcharMbcsConvertor& wmc = WcharMbcsConvertor::getInstance();
 	const wchar_t* lexerNameW = wmc.char2wchar(externalLexer._name.c_str(), CP_ACP);
 	LexerStyler *pStyler = (NppParameters::getInstance().getLStylerArray()).getLexerStylerByName(lexerNameW);
diff --git a/PowerEditor/src/resource.h b/PowerEditor/src/resource.h
index 7b1592d5a..b73238862 100644
--- a/PowerEditor/src/resource.h
+++ b/PowerEditor/src/resource.h
@@ -649,6 +649,7 @@
 	#define NPPM_INTERNAL_NPCFORMCHANGED                (NOTEPADPLUS_USER_INTERNAL + 73)
 	#define NPPM_INTERNAL_NPCLAUNCHSTYLECONF            (NOTEPADPLUS_USER_INTERNAL + 74)
 	#define NPPM_INTERNAL_CLOSEDOC                      (NOTEPADPLUS_USER_INTERNAL + 75)
+	#define NPPM_INTERNAL_EXTERNALLEXERBUFFER           (NOTEPADPLUS_USER_INTERNAL + 76)
 
 // See Notepad_plus_msgs.h
 //#define NOTEPADPLUS_USER   (WM_USER + 1000)