diff --git a/src/ddsurface.c b/src/ddsurface.c
index feeb90a..d1a1b24 100644
--- a/src/ddsurface.c
+++ b/src/ddsurface.c
@@ -1046,6 +1046,8 @@ HRESULT dds_SetColorKey(IDirectDrawSurfaceImpl* This, DWORD dwFlags, LPDDCOLORKE
 
     if (lpColorKey)
     {
+        This->flags |= DDSD_CKSRCBLT;
+
         This->color_key.dwColorSpaceLowValue = lpColorKey->dwColorSpaceLowValue;
 
         if (dwFlags & DDCKEY_COLORSPACE)