@@ -149,6 +149,11 @@ func (store *store) addReference(ref reference.Named, id digest.Digest, force bo

 	oldID, exists := repository[refStr]

 	if exists {

+		if oldID == id {

+			// Nothing to do. The caller may have checked for this using store.Get in advance, but store.mu was unlocked in the meantime, so this can legitimately happen nevertheless.

+			return nil

+		}

+

 		// force only works for tags

 		if digested, isDigest := ref.(reference.Canonical); isDigest {

 			return errors.WithStack(conflictingTagError("Cannot overwrite digest " + digested.Digest().String()))

@@ -163,6 +163,10 @@ func TestAddDeleteGet(t *testing.T) {

 	if err = store.AddTag(ref4, testImageID2, false); err != nil {

 		t.Fatalf("error adding to store: %v", err)

 	}

+	// Write the same values again; should silently succeed

+	if err = store.AddTag(ref4, testImageID2, false); err != nil {

+		t.Fatalf("error redundantly adding to store: %v", err)

+	}

 	ref5, err := reference.ParseNormalizedNamed("username/repo3@sha256:58153dfb11794fad694460162bf0cb0a4fa710cfa3f60979c177d920813e267c")

 	if err != nil {

@@ -171,6 +175,10 @@ func TestAddDeleteGet(t *testing.T) {

 	if err = store.AddDigest(ref5.(reference.Canonical), testImageID2, false); err != nil {

 		t.Fatalf("error adding to store: %v", err)

 	}

+	// Write the same values again; should silently succeed

+	if err = store.AddDigest(ref5.(reference.Canonical), testImageID2, false); err != nil {

+		t.Fatalf("error redundantly adding to store: %v", err)

+	}

 	// Attempt to overwrite with force == false

 	if err = store.AddTag(ref4, testImageID3, false); err == nil || !strings.HasPrefix(err.Error(), "Conflict:") {