diff --git a/wiki/storage/mongo/storage.go b/wiki/storage/mongo/storage.go
index 6209b7f..d5165c9 100644
--- a/wiki/storage/mongo/storage.go
+++ b/wiki/storage/mongo/storage.go
@@ -9,7 +9,7 @@ import (
 const (
 	databaseDefault          = "wiki"
 	termCollectionDefault    = "term"
-	RevisionCollectionDefault = "revision"
+	revisionCollectionDefault = "revision"
 )
 
 type mongoStorage struct {
@@ -33,7 +33,7 @@ func New(ms *mgo.Session, config Config) mongoStorage {
 		config.TermCollection = termCollectionDefault
 	}
 	if config.RevisionCollection == "" {
-		config.RevisionCollection = RevisionCollectionDefault
+		config.RevisionCollection = revisionCollectionDefault
 	}
 
 	return mongoStorage{
diff --git a/wiki/template/renderer.go b/wiki/template/renderer.go
index f73fd53..df00826 100644
--- a/wiki/template/renderer.go
+++ b/wiki/template/renderer.go
@@ -45,7 +45,9 @@ func (r *Renderer) Render(w io.Writer, name string, data interface{}) error {
 	}
 	ctx, ok := data.(map[string]interface{})
 	if !ok {
-		return errors.New("data is compatible with map[string]interface{}")
+		if data != nil {
+			return errors.New("data is not compatible with map[string]interface{}")
+		}
 	}
 	return t.ExecuteWriter(ctx, w)
 }