diff --git a/libs/ardour/ardour/comparable_shared_ptr.h b/libs/ardour/ardour/comparable_shared_ptr.h
index 32cdfc21a2..a49481fe08 100644
--- a/libs/ardour/ardour/comparable_shared_ptr.h
+++ b/libs/ardour/ardour/comparable_shared_ptr.h
@@ -42,7 +42,10 @@ class /*LIBARDOUR_API*/ ComparableSharedPtr : public boost::shared_ptr<T>
 
 	ComparableSharedPtr (ComparableSharedPtr const & r) : boost::shared_ptr<T> (r) {}
 
-	ComparableSharedPtr& operator=(const ComparableSharedPtr& r) { *this = r; return *this; }
+	ComparableSharedPtr& operator=(ComparableSharedPtr const& r) BOOST_SP_NOEXCEPT {
+		boost::shared_ptr<T>(r).swap(*this);
+		return *this;
+	}
 
 	template<class Y>
 	ComparableSharedPtr(ComparableSharedPtr<Y> const & r) : boost::shared_ptr<T> (r) {}