update regression results
diff --git a/Makefile b/Makefile
index 83ab37d..9b5451d 100644
--- a/Makefile
+++ b/Makefile
@@ -298,7 +298,7 @@
         --output $(REGRESS_RESULTS_DIR)/results.csv \
         --zstd   programs/zstd
 	echo "Showing results differences"
-	diff tests/regression/results.csv $(REGRESS_RESULTS_DIR)/results.csv
+	! diff tests/regression/results.csv $(REGRESS_RESULTS_DIR)/results.csv
 	echo "Updating results.csv"
 	$(CP) $(REGRESS_RESULTS_DIR)/results.csv tests/regression/results.csv