diff --git a/quiche/common/structured_headers.h b/quiche/common/structured_headers.h
index 9c29b1b..c86c13f 100644
--- a/quiche/common/structured_headers.h
+++ b/quiche/common/structured_headers.h
@@ -175,7 +175,7 @@
 // Token, and there may be any number of parameters. Parameter ordering is not
 // significant.
 struct QUICHE_EXPORT ParameterisedIdentifier {
-  using Parameters = std::map<std::string, Item>;
+  using Parameters = std::map<std::string, Item, std::less<>>;
 
   Item identifier;
   Parameters params;