diff --git a/internal/registry/configfile.go b/internal/registry/configfile.go
index 4a8421e2..268faa57 100644
--- a/internal/registry/configfile.go
+++ b/internal/registry/configfile.go
@@ -12,7 +12,7 @@ import (
 	"github.com/pkg/errors"
 )
 
-// This is ported from https://github.com/docker/cli/blob/v20.10.12/cli/config/config.go
+// This is ported from https://github.com/docker/cli/blob/v20.10.15/cli/config/configfile/file.go
 // The only changes to the original source are the fact, that the "auth" field is not decoded
 // when "username" or "password" are not blank to avoid overwrites.
 
diff --git a/internal/registry/configfile_test.go b/internal/registry/configfile_test.go
new file mode 100644
index 00000000..8c17302b
--- /dev/null
+++ b/internal/registry/configfile_test.go
@@ -0,0 +1,65 @@
+package registry
+
+import (
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"github.com/docker/cli/cli/config"
+	"github.com/docker/cli/cli/config/configfile"
+	"github.com/docker/cli/cli/config/types"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestOldJSONReaderNoFile(t *testing.T) {
+	js := `{"https://index.docker.io/v1/":{"auth":"am9lam9lOmhlbGxv","email":"user@example.com"}}`
+	configFile := configfile.ConfigFile{
+		AuthConfigs: make(map[string]types.AuthConfig),
+	}
+
+	err := LegacyLoadFromReader(strings.NewReader(js), &configFile)
+	assert.Nil(t, err)
+
+	ac := configFile.AuthConfigs["https://index.docker.io/v1/"]
+	assert.Equal(t, ac.Username, "joejoe")
+	assert.Equal(t, ac.Password, "hello")
+}
+
+func TestLegacyJSONSaveWithNoFile(t *testing.T) {
+	js := `{"https://index.docker.io/v1/":{"auth":"am9lam9lOmhlbGxv","email":"user@example.com"}}`
+	configFile := configfile.ConfigFile{
+		AuthConfigs: make(map[string]types.AuthConfig),
+	}
+
+	err := LegacyLoadFromReader(strings.NewReader(js), &configFile)
+	assert.Nil(t, err)
+	err = configFile.Save()
+	assert.ErrorContains(t, err, "with empty filename")
+
+	tmpHome, err := ioutil.TempDir("", "config-test")
+	assert.Nil(t, err)
+	defer os.RemoveAll(tmpHome)
+
+	fn := filepath.Join(tmpHome, config.ConfigFileName)
+	f, _ := os.OpenFile(fn, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0600)
+	defer f.Close()
+
+	assert.Nil(t, configFile.SaveToWriter(f))
+	buf, err := ioutil.ReadFile(filepath.Join(tmpHome, config.ConfigFileName))
+	assert.Nil(t, err)
+
+	expConfStr := `{
+	"auths": {
+		"https://index.docker.io/v1/": {
+			"auth": "am9lam9lOmhlbGxv",
+			"email": "user@example.com"
+		}
+	}
+}`
+
+	if string(buf) != expConfStr {
+		t.Fatalf("Should have save in new form: \n%s\n not \n%s", string(buf), expConfStr)
+	}
+}