diff --git a/win32ss/gdi/ntgdi/bitmaps.c b/win32ss/gdi/ntgdi/bitmaps.c
index 0f556f9b916..59fb5dd9d15 100644
--- a/win32ss/gdi/ntgdi/bitmaps.c
+++ b/win32ss/gdi/ntgdi/bitmaps.c
@@ -645,7 +645,7 @@ NtGdiSetBitmapBits(
     _SEH2_TRY
     {
         /* NOTE: Win2k3 doesn't check WORD alignment here. */
-        ProbeForRead(pUnsafeBits, Bytes, 1);
+        ProbeForWrite(pUnsafeBits, Bytes, 1);
         ret = UnsafeSetBitmapBits(psurf, Bytes, pUnsafeBits);
     }
     _SEH2_EXCEPT(EXCEPTION_EXECUTE_HANDLER)