diff --git a/mutation.cc b/mutation.cc
index 16547e4756..a67b278e85 100644
--- a/mutation.cc
+++ b/mutation.cc
@@ -111,3 +111,8 @@ size_t
 mutation::live_row_count(gc_clock::time_point query_time) const {
     return _p.live_row_count(*_schema, query_time);
 }
+
+bool
+mutation_decorated_key_less_comparator::operator()(const mutation& m1, const mutation& m2) const {
+    return m1.decorated_key().less_compare(*m1.schema(), m2.decorated_key());
+}
diff --git a/mutation.hh b/mutation.hh
index 6a84f491e5..a28163b777 100644
--- a/mutation.hh
+++ b/mutation.hh
@@ -50,6 +50,10 @@ private:
     friend std::ostream& operator<<(std::ostream& os, const mutation& m);
 };
 
+struct mutation_decorated_key_less_comparator {
+    bool operator()(const mutation& m1, const mutation& m2) const;
+};
+
 using mutation_opt = std::experimental::optional<mutation>;
 
 inline