diff --git a/src/policy_cache.hpp b/src/policy_cache.hpp
index a5f5d6cd..067bdd37 100644
--- a/src/policy_cache.hpp
+++ b/src/policy_cache.hpp
@@ -52,7 +52,7 @@ public:
     nonstd::optional<std::string> rv;
 
     auto func =
-      [&](const std::string &v_)
+      [&](std::string &v_)
       {
         rv = v_;
       };