diff --git a/go/src/bashbrew/docker.go b/go/src/bashbrew/docker.go
index f0057c2..f3deeb4 100644
--- a/go/src/bashbrew/docker.go
+++ b/go/src/bashbrew/docker.go
@@ -151,10 +151,10 @@ func dockerTag(tag1 string, tag2 string) error {
 	if debugFlag {
 		fmt.Printf("$ docker tag %q %q\n", tag1, tag2)
 	}
-	_, err := exec.Command("docker", "tag", "-f", tag1, tag2).Output()
+	_, err := exec.Command("docker", "tag", tag1, tag2).Output()
 	if err != nil {
 		if ee, ok := err.(*exec.ExitError); ok {
-			return fmt.Errorf("%v\ncommand: docker tag -f %q %q\n%s", ee, tag1, tag2, string(ee.Stderr))
+			return fmt.Errorf("%v\ncommand: docker tag %q %q\n%s", ee, tag1, tag2, string(ee.Stderr))
 		}
 	}
 	return err