diff --git a/provider.go b/provider.go
index 4dac5df..1a8db3e 100644
--- a/provider.go
+++ b/provider.go
@@ -36,6 +36,11 @@ type Trimmer interface {
 	Trim ()
 }
 
+// Initializer is an object that must be initialized before first use.
+type Initializer interface {
+	Init () error
+}
+
 // FuncProvider provides a template.FuncMap.
 type FuncProvider interface {
 	Provider