diff --git a/test/rb/Makefile b/test/rb/Makefile
index 502a981..326f720 100644
--- a/test/rb/Makefile
+++ b/test/rb/Makefile
@@ -19,4 +19,4 @@
 	ruby TestSuite.rb
 
 clean:
-	rm -fr gen-rb
+	$(RM) -r gen-rb