diff --git a/PowerEditor/src/WinControls/DockingWnd/DockingSplitter.cpp b/PowerEditor/src/WinControls/DockingWnd/DockingSplitter.cpp
index 0c46ce93b..ca1f3ebd8 100644
--- a/PowerEditor/src/WinControls/DockingWnd/DockingSplitter.cpp
+++ b/PowerEditor/src/WinControls/DockingWnd/DockingSplitter.cpp
@@ -32,7 +32,7 @@ void DockingSplitter::init(HINSTANCE hInst, HWND hWnd, HWND hMessage, UINT flags
 
 	WNDCLASS wc;
 	DWORD hwndExStyle = (DWORD)GetWindowLongPtr(hWnd, GWL_EXSTYLE);
-	isRTL = hwndExStyle & WS_EX_LAYOUTRTL;
+	_isRTL = hwndExStyle & WS_EX_LAYOUTRTL;
 
 	if (flags & DMS_HORIZONTAL)
 	{
@@ -139,7 +139,7 @@ LRESULT DockingSplitter::runProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM
 				}
 				else if (_ptOldPos.x != pt.x)
 				{
-					::SendMessage(_hMessage, DMM_MOVE_SPLITTER, isRTL ? pt.x - _ptOldPos.x : _ptOldPos.x - pt.x, reinterpret_cast<LPARAM>(_hSelf));
+					::SendMessage(_hMessage, DMM_MOVE_SPLITTER, _isRTL ? pt.x - _ptOldPos.x : _ptOldPos.x - pt.x, reinterpret_cast<LPARAM>(_hSelf));
 				}
 				_ptOldPos = pt;
 			}
diff --git a/PowerEditor/src/WinControls/DockingWnd/DockingSplitter.h b/PowerEditor/src/WinControls/DockingWnd/DockingSplitter.h
index b1085ce5a..ea98c9b68 100644
--- a/PowerEditor/src/WinControls/DockingWnd/DockingSplitter.h
+++ b/PowerEditor/src/WinControls/DockingWnd/DockingSplitter.h
@@ -51,6 +51,6 @@ private:
 	static BOOL _isHoriReg;
 
 	// get layout direction
-	bool isRTL;
+	bool _isRTL = false;
 };