diff --git a/reactos/subsystems/win32/win32k/dib/stretchblt.c b/reactos/subsystems/win32/win32k/dib/stretchblt.c
index 45a5b8f826b..914d6722a9a 100644
--- a/reactos/subsystems/win32/win32k/dib/stretchblt.c
+++ b/reactos/subsystems/win32/win32k/dib/stretchblt.c
@@ -43,11 +43,11 @@ BOOLEAN DIB_XXBPP_StretchBlt(SURFOBJ *DestSurf, SURFOBJ *SourceSurf, SURFOBJ *Ma
 
   LONG PatternX = 0, PatternY = 0;
 
-  ASSERT(IS_VALID_ROP4(ROP));
-
   BOOL UsesSource = ROP4_USES_SOURCE(ROP);
   BOOL UsesPattern = ROP4_USES_PATTERN(ROP);
 
+  ASSERT(IS_VALID_ROP4(ROP));
+
   fnDest_GetPixel = DibFunctionsForBitmapFormat[DestSurf->iBitmapFormat].DIB_GetPixel;
   fnDest_PutPixel = DibFunctionsForBitmapFormat[DestSurf->iBitmapFormat].DIB_PutPixel;