diff --git a/dlls/wined3d/wined3d_private.h b/dlls/wined3d/wined3d_private.h
index d735bb5..7743051 100644
--- a/dlls/wined3d/wined3d_private.h
+++ b/dlls/wined3d/wined3d_private.h
@@ -2057,6 +2057,6 @@
 }
 
 void stretch_rect_fbo(IWineD3DDevice *iface, IWineD3DSurface *src_surface, WINED3DRECT *src_rect,
-        IWineD3DSurface *dst_surface, WINED3DRECT *dst_rect, WINED3DTEXTUREFILTERTYPE filter, BOOL flip);
+        IWineD3DSurface *dst_surface, WINED3DRECT *dst_rect, const WINED3DTEXTUREFILTERTYPE filter, BOOL flip);
 
 #endif