diff --git a/map/fixed.hpp b/map/fixed.hpp
index 2e46e659..bff0803a 100644
--- a/map/fixed.hpp
+++ b/map/fixed.hpp
@@ -112,6 +112,17 @@ namespace cruft::map {
         }
 
 
+        //---------------------------------------------------------------------
+        mapped_type const& operator[] (KeyT const &key) const
+        {
+            ComparatorT cmp {};
+            for (auto &i: *this)
+                if (cmp (i.first, key))
+                    return i.second;
+            throw std::out_of_range ("Invalid key");
+        }
+
+
         //---------------------------------------------------------------------
         mapped_type& operator[] (KeyT const &key)
         {