diff --git a/aidl_language.h b/aidl_language.h
index 4f24da7..052ba77 100644
--- a/aidl_language.h
+++ b/aidl_language.h
@@ -205,7 +205,7 @@
     std::string name;
 
     // map from param name -> value type
-    std::map<std::string, std::string> supported_parameters;
+    std::map<std::string, const AidlTypeSpecifier&> supported_parameters;
 
     bool repeatable;