diff --git a/vcl/source/bitmap/BitmapMosaicFilter.cxx b/vcl/source/bitmap/BitmapMosaicFilter.cxx
index c13ab0199540..0426dc3ff044 100644
--- a/vcl/source/bitmap/BitmapMosaicFilter.cxx
+++ b/vcl/source/bitmap/BitmapMosaicFilter.cxx
@@ -156,8 +156,9 @@ BitmapEx BitmapMosaicFilter::execute(BitmapEx const& rBitmapEx) const
             bRet = true;
         }
 
+        if (pWriteAcc == pReadAcc)
+            pWriteAcc = nullptr;
         Bitmap::ReleaseAccess(pReadAcc);
-        pReadAcc = nullptr;
 
         if (pNewBmp)
         {