diff --git a/reactos/subsystems/win32/win32k/include/dc.h b/reactos/subsystems/win32/win32k/include/dc.h
index ef25e5e8f79..dfc73e15c0f 100644
--- a/reactos/subsystems/win32/win32k/include/dc.h
+++ b/reactos/subsystems/win32/win32k/include/dc.h
@@ -4,6 +4,9 @@
 
 #include "driver.h"
 
+// Get/SetBounds/Rect support.
+#define DCB_WINDOWMGR 0x8000 // Queries the Windows bounding rectangle instead of the application's
+
   /* DC flags */
 #define DC_SAVED      0x0002   /* It is a saved DC */
 #define DC_DIRTY      0x0004   /* hVisRgn has to be updated */