diff --git a/src/util/ue2_containers.h b/src/util/ue2_containers.h
index 672cb811..75e0a0a4 100644
--- a/src/util/ue2_containers.h
+++ b/src/util/ue2_containers.h
@@ -611,6 +611,21 @@ public:
         return comp();
     }
 
+    class value_compare {
+        friend class flat_map;
+    protected:
+        Compare c;
+        value_compare(Compare c_in) : c(c_in) {}
+    public:
+        bool operator()(const value_type &lhs, const value_type &rhs) {
+            return c(lhs.first, rhs.first);
+        }
+    };
+
+    value_compare value_comp() const {
+        return value_compare(comp());
+    }
+
     // Operators.
 
     bool operator==(const flat_map &a) const {
diff --git a/unit/internal/flat_map.cpp b/unit/internal/flat_map.cpp
index 966a5d8f..6a81bbfe 100644
--- a/unit/internal/flat_map.cpp
+++ b/unit/internal/flat_map.cpp
@@ -211,6 +211,7 @@ TEST(flat_map, custom_compare) {
     ASSERT_EQ(10, f.rbegin()->second);
 
     ASSERT_TRUE(flat_map_is_sorted(f));
+    ASSERT_TRUE(std::is_sorted(f.begin(), f.end(), f.value_comp()));
     ASSERT_TRUE(flat_map_is_sorted_cmp(f, std::greater<u32>()));
 }