@@ -321,7 +321,11 @@ func (p *puller) CacheKey(ctx context.Context, index int) (string, bool, error)

 	}

 	if p.config != nil {

-		return cacheKeyFromConfig(p.config).String(), true, nil

+		k := cacheKeyFromConfig(p.config).String()

+		if k == "" {

+			return digest.FromBytes(p.config).String(), true, nil

+		}

+		return k, true, nil

 	}

 	if err := p.resolve(ctx); err != nil {

@@ -336,7 +340,16 @@ func (p *puller) CacheKey(ctx context.Context, index int) (string, bool, error)

 		return dgst.String(), false, nil

 	}

-	return cacheKeyFromConfig(p.config).String(), true, nil

+	k := cacheKeyFromConfig(p.config).String()

+	if k == "" {

+		dgst, err := p.mainManifestKey(p.desc.Digest, p.platform)

+		if err != nil {

+			return "", false, err

+		}

+		return dgst.String(), true, nil

+	}

+

+	return k, true, nil

 }

 func (p *puller) Snapshot(ctx context.Context) (cache.ImmutableRef, error) {

@@ -776,8 +789,8 @@ func cacheKeyFromConfig(dt []byte) digest.Digest {

 	if err != nil {

 		return digest.FromBytes(dt)

 	}

-	if img.RootFS.Type != "layers" {

-		return digest.FromBytes(dt)

+	if img.RootFS.Type != "layers" || len(img.RootFS.DiffIDs) == 0 {

+		return ""

 	}

 	return identity.ChainID(img.RootFS.DiffIDs)

 }