can't const a ReferenceType (clang)

Index: src/shared/sharedptr.h
--- src/shared/sharedptr.h.orig
+++ src/shared/sharedptr.h
@@ -181,7 +181,7 @@ class SharedPtr { (public)
 		return *_pointer < *other;
 	}
 
-	inline bool operator< (const ReferenceType other) const
+	inline bool operator< (ReferenceType other) const
 	{
 		return *_pointer < other;
 	}
