diff --git a/internal/api.go b/internal/api.go
index 047793e..aa139d4 100644
--- a/internal/api.go
+++ b/internal/api.go
@@ -231,7 +231,7 @@ func fromContext(ctx netcontext.Context) *context {
 func withContext(parent netcontext.Context, c *context) netcontext.Context {
 	ctx := netcontext.WithValue(parent, &contextKey, c)
 	if ns := c.req.Header.Get(curNamespaceHeader); ns != "" {
-		ctx = WithNamespace(ctx, ns)
+		ctx = withNamespace(ctx, ns)
 	}
 	return ctx
 }
diff --git a/internal/api_classic.go b/internal/api_classic.go
index b40dd70..1c072e9 100644
--- a/internal/api_classic.go
+++ b/internal/api_classic.go
@@ -37,7 +37,7 @@ func withContext(parent netcontext.Context, c appengine.Context) netcontext.Cont
 	s := &basepb.StringProto{}
 	c.Call("__go__", "GetNamespace", &basepb.VoidProto{}, s, nil)
 	if ns := s.GetValue(); ns != "" {
-		ctx = WithNamespace(ctx, ns)
+		ctx = NamespacedContext(ctx, ns)
 	}
 
 	return ctx
diff --git a/internal/api_common.go b/internal/api_common.go
index 51c4dd4..ec5383e 100644
--- a/internal/api_common.go
+++ b/internal/api_common.go
@@ -52,7 +52,7 @@ func WithAppIDOverride(ctx netcontext.Context, appID string) netcontext.Context
 
 var namespaceKey = "holds the namespace string"
 
-func WithNamespace(ctx netcontext.Context, ns string) netcontext.Context {
+func withNamespace(ctx netcontext.Context, ns string) netcontext.Context {
 	return netcontext.WithValue(ctx, &namespaceKey, ns)
 }
 
@@ -79,3 +79,23 @@ func Logf(ctx netcontext.Context, level int64, format string, args ...interface{
 	}
 	logf(fromContext(ctx), level, format, args...)
 }
+
+// NamespacedContext wraps a Context to support namespaces.
+func NamespacedContext(ctx netcontext.Context, namespace string) netcontext.Context {
+	n := &namespacedContext{
+		namespace: namespace,
+	}
+	return withNamespace(WithCallOverride(ctx, n.call), namespace)
+}
+
+type namespacedContext struct {
+	namespace string
+}
+
+func (n *namespacedContext) call(ctx netcontext.Context, service, method string, in, out proto.Message) error {
+	// Apply any namespace mods.
+	if mod, ok := NamespaceMods[service]; ok {
+		mod(in, n.namespace)
+	}
+	return Call(ctx, service, method, in, out)
+}
diff --git a/namespace.go b/namespace.go
index 65b0a00..21860ca 100644
--- a/namespace.go
+++ b/namespace.go
@@ -8,7 +8,6 @@ import (
 	"fmt"
 	"regexp"
 
-	"github.com/golang/protobuf/proto"
 	"golang.org/x/net/context"
 
 	"google.golang.org/appengine/internal"
@@ -19,24 +18,8 @@ func Namespace(c context.Context, namespace string) (context.Context, error) {
 	if !validNamespace.MatchString(namespace) {
 		return nil, fmt.Errorf("appengine: namespace %q does not match /%s/", namespace, validNamespace)
 	}
-	n := &namespacedContext{
-		namespace: namespace,
-	}
-	return internal.WithNamespace(internal.WithCallOverride(c, n.call), namespace), nil
+	return internal.NamespacedContext(c, namespace), nil
 }
 
 // validNamespace matches valid namespace names.
 var validNamespace = regexp.MustCompile(`^[0-9A-Za-z._-]{0,100}$`)
-
-// namespacedContext wraps a Context to support namespaces.
-type namespacedContext struct {
-	namespace string
-}
-
-func (n *namespacedContext) call(ctx context.Context, service, method string, in, out proto.Message) error {
-	// Apply any namespace mods.
-	if mod, ok := internal.NamespaceMods[service]; ok {
-		mod(in, n.namespace)
-	}
-	return internal.Call(ctx, service, method, in, out)
-}