diff --git a/Makefile b/Makefile
index b211123..fb086eb 100644
--- a/Makefile
+++ b/Makefile
@@ -48,7 +48,7 @@ clean:
 	@rm -fv $(EXEC) gmon.out output.png
 
 mrproper: clean
-	@rm -rv $(OBJ_DIR)
+	@rm -frv $(OBJ_DIR)
 
 .PHONY: check-env
 check-env: check-gprof2dot-works check-gprof-works check-gdb-works check-valgrind-works check-r2-works