diff --git a/mmv.go b/mmv.go
index 4b2a12b..5cf5731 100644
--- a/mmv.go
+++ b/mmv.go
@@ -39,7 +39,7 @@ func doRename(src, dst string) (err error) {
 			return err
 		}
 		// create the destination directory
-		if err := os.MkdirAll(filepath.Dir(dst), 0755); err != nil {
+		if err := os.MkdirAll(filepath.Dir(dst), 0o755); err != nil {
 			return err
 		}
 		// try renaming again
diff --git a/mmv_test.go b/mmv_test.go
index b41e300..2d8e270 100644
--- a/mmv_test.go
+++ b/mmv_test.go
@@ -320,7 +320,7 @@ func TestRename(t *testing.T) {
 
 func setupFiles(contents map[string]string) error {
 	for f, cnt := range contents {
-		if err := ioutil.WriteFile(f, []byte(cnt), 0600); err != nil {
+		if err := ioutil.WriteFile(f, []byte(cnt), 0o600); err != nil {
 			return err
 		}
 	}