diff --git a/pngwutil.c b/pngwutil.c
index 2e4d1a5..665464b 100644
--- a/pngwutil.c
+++ b/pngwutil.c
@@ -2448,7 +2448,7 @@
       /* Overflow can occur in the calculation, just select the lowest set
        * filter.
        */
-      filter_to_do &= -filter_to_do;
+      filter_to_do &= 0U-filter_to_do;
    }
    else if ((filter_to_do & PNG_FILTER_NONE) != 0 &&
          filter_to_do != PNG_FILTER_NONE)