diff --git a/cmd/app/kodata/index.html b/cmd/app/kodata/index.html
index 4a872d2..69f7ac4 100644
--- a/cmd/app/kodata/index.html
+++ b/cmd/app/kodata/index.html
@@ -22,13 +22,13 @@ bytes.  You can request a specific size and shape of random image. For example,
 
 <h1><code>ko.kontain.me</code></h1>
 
-<p><code>docker pull ko.kontain.me/ko/[import path]</code> serves an image
+<p><code>docker pull ko.kontain.me/[import path]</code> serves an image
 containing a Go binary fetched using <code>go get</code> and built into a
 container image using <a
 	href="https://github.com/google/ko"><code>ko</code></a>.</p>
 
 <p>For example,
-<code>docker pull ko.kontain.me/ko/github.com/google/ko/cmd/ko</code> will fetch,
+<code>docker pull ko.kontain.me/github.com/google/ko/cmd/ko</code> will fetch,
 build and (eventually) serve a Docker image containing <code>ko</code> itself.
 <i>Koception!</i></p>
 
diff --git a/cmd/ko/main.go b/cmd/ko/main.go
index b17d810..190083d 100644
--- a/cmd/ko/main.go
+++ b/cmd/ko/main.go
@@ -76,20 +76,24 @@ func (s *server) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	case strings.Contains(path, "/manifests/"):
 		s.serveKoManifest(w, r)
 	default:
-		serve.Error(w, serve.ErrNotFound)
+		http.Error(w, "Not found", http.StatusNotFound)
 	}
 }
 
-// konta.in/ko/github.com/knative/build/cmd/controller -> ko build and serve
+// ko.kontain.me/github.com/knative/build/cmd/controller -> ko build and serve
 func (s *server) serveKoManifest(w http.ResponseWriter, r *http.Request) {
-	path := strings.TrimPrefix(r.URL.Path, "/v2/ko/")
+	path := strings.TrimPrefix(r.URL.Path, "/v2/")
+	path = strings.TrimPrefix(path, "ko/") // To handle legacy behavior.
 	parts := strings.Split(path, "/")
 	ip := strings.Join(parts[:len(parts)-2], "/")
 
+	// "go get" the package
 	tag := parts[len(parts)-1]
 	s.info.Printf("requested image tag :%s", tag)
 
 	// go get the package.
+	// TODO: Check image tag for version, resolve branches -> commits and redirect to img:<commit>
+	// TODO: For requests for commit SHAs, check if it's already built and serve that instead.
 	s.info.Printf("go get %s...", ip)
 	if err := run.Do(s.info.Writer(), fmt.Sprintf("go get %s", ip)); err != nil {
 		s.error.Printf("ERROR (go get): %s", err)
@@ -97,9 +101,6 @@ func (s *server) serveKoManifest(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	// TODO: Check image tag for version, resolve branches -> commits and redirect to img:<commit>
-	// TODO: For requests for commit SHAs, check if it's already built and serve that instead.
-
 	// ko build the package.
 	g, err := build.NewGo(
 		build.WithBaseImages(s.getBaseImage),
@@ -107,20 +108,20 @@ func (s *server) serveKoManifest(w http.ResponseWriter, r *http.Request) {
 	)
 	if err != nil {
 		s.error.Printf("ERROR (build.NewGo): %s", err)
-		serve.Error(w, serve.ErrInvalid)
+		serve.Error(w, err)
 		return
 	}
 	ip = build.StrictScheme + ip
 	if !g.IsSupportedReference(ip) {
 		s.error.Printf("ERROR (IsSupportedReference(%q)): false", ip)
-		serve.Error(w, serve.ErrInvalid)
+		serve.Error(w, fmt.Errorf("Import path %q is not package main", ip))
 		return
 	}
 	s.info.Printf("ko build %s...", ip)
 	br, err := g.Build(context.Background(), ip)
 	if err != nil {
 		s.error.Printf("ERROR (ko build): %s", err)
-		serve.Error(w, serve.ErrInvalid)
+		serve.Error(w, err)
 		return
 	}
 	if idx, ok := br.(v1.ImageIndex); ok {
diff --git a/pkg/serve/error.go b/pkg/serve/error.go
index 42f1975..37fe519 100644
--- a/pkg/serve/error.go
+++ b/pkg/serve/error.go
@@ -8,13 +8,10 @@ import (
 	"github.com/google/go-containerregistry/pkg/v1/remote/transport"
 )
 
-var (
-	ErrNotFound = errors.New("repository or commit not found")
-	ErrInvalid  = errors.New("requested manifest is invalid")
-)
+var ErrNotFound = errors.New("repository or commit not found")
 
 func Error(w http.ResponseWriter, err error) {
-	code := "INTERNAL_ERROR"
+	code := "MANIFEST_UNKNOWN"
 	httpCode := http.StatusNotFound
 	if terr, ok := err.(*transport.Error); ok {
 		http.Error(w, "", terr.StatusCode)
@@ -22,13 +19,6 @@ func Error(w http.ResponseWriter, err error) {
 		return
 	}
 
-	if err == ErrNotFound {
-		code = "MANIFEST_UNKNOWN"
-	} else if err == ErrInvalid {
-		code = "NAME_INVALID"
-		httpCode = http.StatusBadRequest
-	}
-
 	http.Error(w, "", httpCode)
 	json.NewEncoder(w).Encode(&resp{
 		Errors: []e{{