diff --git a/addon/IdentityManager.idl b/addon/IdentityManager.idl
index 135d2c3..55db019 100644
--- a/addon/IdentityManager.idl
+++ b/addon/IdentityManager.idl
@@ -42,7 +42,7 @@ interface nsIIdentityManager : nsISupports {
   void createSignInButton(in nsIVariant providers,
                           in nsIVariant attributes,
                           in nsIVariant domID,
-                          in nsiVariant callback);
+                          in nsIVariant callback);
 
   /* Bogus method for testing. */
   AString foo();