diff --git a/cmd/pkg.go b/cmd/pkg.go
index 7cd442b523a0b69408e5dee10c8133beb7a8a7b7..afd2f188ba7683a3efb26e774757c6e5f89ad599 100644
--- a/cmd/pkg.go
+++ b/cmd/pkg.go
@@ -249,7 +249,10 @@ func parseDepSpec(cmd *cobra.Command, spec string) (registry, libID, name, versi
 	if len(split) > 2 {
 		return "", "", "", "", fmt.Errorf("Symbol '@' is only allowed once, at the end of the argument of the form <registry>/<library>@<version>")
 	}
-	version = split[len(split)-1]
+	version = ""
+	if len(split) == 2 {
+		version = split[1]
+	}
 
 	name, err = cmd.Flags().GetString(flagName)
 	if err != nil {
diff --git a/metadata/interface.go b/metadata/interface.go
index b86c4983a78a00d25f2b3384d2fc548df8871967..560e4faacd3d1da34c63970b77209b917b82e1af 100644
--- a/metadata/interface.go
+++ b/metadata/interface.go
@@ -96,7 +96,7 @@ func Init(name string, rootPath AbsPath, spec ClusterSpec, serverURI, namespace
 	// directory tree, in case the network call fails.
 	const (
 		defaultIncubatorRegName = "incubator"
-		defaultIncubatorURI     = "github.com/ksonnet/parts/tree/test-reg/" + defaultIncubatorRegName
+		defaultIncubatorURI     = "github.com/ksonnet/parts/tree/master/" + defaultIncubatorRegName
 	)
 
 	gh, err := makeGitHubRegistryManager(&app.RegistryRefSpec{
diff --git a/metadata/registry_managers.go b/metadata/registry_managers.go
index 9ea7645a1eca307ebfa13d0ebb7d1dbce788ecb7..c07adff1845eb0b17ec20fdd502ba2d617b812ac 100644
--- a/metadata/registry_managers.go
+++ b/metadata/registry_managers.go
@@ -152,10 +152,17 @@ func (gh *gitHubRegistryManager) ResolveLibrarySpec(libID, libRefSpec string) (*
 }
 
 func (gh *gitHubRegistryManager) ResolveLibrary(libID, libAlias, libRefSpec string, onFile registry.ResolveFile, onDir registry.ResolveDirectory) (*parts.Spec, *app.LibraryRefSpec, error) {
+	const (
+		defaultRefSpec = "master"
+	)
+
 	client := github.NewClient(nil)
 
 	// Resolve `version` (a git refspec) to a specific SHA.
 	ctx := context.Background()
+	if len(libRefSpec) == 0 {
+		libRefSpec = defaultRefSpec
+	}
 	resolvedSHA, _, err := client.Repositories.GetCommitSHA1(ctx, gh.org, gh.repo, libRefSpec, "")
 	if err != nil {
 		return nil, nil, err