diff --git a/indra/llcommon/llheteromap.h b/indra/llcommon/llheteromap.h
index 9d6f303d08beb261fe4df04db426d5d320397c1c..7e96172333293340840af4b9b0e1ad2ccb3fb914 100644
--- a/indra/llcommon/llheteromap.h
+++ b/indra/llcommon/llheteromap.h
@@ -77,7 +77,7 @@ class LLHeteroMap
     // not always equal &typeid(A) in some other part. Use special comparator.
     struct type_info_ptr_comp
     {
-        bool operator()(const std::type_info* lhs, const std::type_info* rhs)
+        bool operator()(const std::type_info* lhs, const std::type_info* rhs) const
         {
             return lhs->before(*rhs);
         }