diff --git a/lib/interface.js b/lib/interface.js
index f918a37..9152da0 100644
--- a/lib/interface.js
+++ b/lib/interface.js
@@ -287,7 +287,7 @@ var extend = ( function( extending )
                 // only called if someone tries to create a new instance of an
                 // interface
                 throw Error(
-                    "Interface" + ( ( iname ) ? ( iname + ' ' ) : '' ) +
+                    "Interface " + ( ( iname ) ? ( iname + ' ' ) : '' ) +
                         " cannot be instantiated"
                 );
             }