diff --git a/src/msw/mdi.cpp b/src/msw/mdi.cpp
index 5d2e46955c..db396ec1a3 100644
--- a/src/msw/mdi.cpp
+++ b/src/msw/mdi.cpp
@@ -696,7 +696,7 @@ bool wxMDIChildFrame::Create(wxMDIParentFrame *parent,
   else
       mcs.cy = CW_USEDEFAULT;
 
-  DWORD msflags = WS_OVERLAPPED | WS_CLIPCHILDREN | WS_THICKFRAME | WS_VISIBLE ;
+  DWORD msflags = WS_OVERLAPPED | WS_CLIPCHILDREN | WS_VISIBLE ;
   if (style & wxMINIMIZE_BOX)
     msflags |= WS_MINIMIZEBOX;
   if (style & wxMAXIMIZE_BOX)