Index: dll/win32/comctl32/tooltips.c
===================================================================
--- dll/win32/comctl32/tooltips.c	(revision 71111)
+++ dll/win32/comctl32/tooltips.c	(working copy)
@@ -259,7 +259,12 @@
 
     hBrush = CreateSolidBrush(infoPtr->clrBk);
 
+#ifdef __REACTOS__
+    /* CORE-11086 */
+    oldBkMode = SetBkMode (hdc, OPAQUE);
+#else
     oldBkMode = SetBkMode (hdc, TRANSPARENT);
+#endif
     SetTextColor (hdc, infoPtr->clrText);
     hOldFont = SelectObject (hdc, infoPtr->hFont);