diff --git a/src/libexpr/include/nix/expr/eval.hh b/src/libexpr/include/nix/expr/eval.hh
index 2640dae39..0c7f9cf09 100644
--- a/src/libexpr/include/nix/expr/eval.hh
+++ b/src/libexpr/include/nix/expr/eval.hh
@@ -191,7 +191,7 @@ std::ostream & operator<<(std::ostream & os, const ValueType t);
 
 struct RegexCache;
 
-std::shared_ptr<RegexCache> makeRegexCache();
+ref<RegexCache> makeRegexCache();
 
 struct DebugTrace
 {
@@ -372,6 +372,7 @@ public:
 
     const fetchers::Settings & fetchSettings;
     const EvalSettings & settings;
+
     SymbolTable symbols;
     PosTable positions;
 
@@ -504,7 +505,7 @@ private:
     /**
      * Cache used by prim_match().
      */
-    std::shared_ptr<RegexCache> regexCache;
+    const ref<RegexCache> regexCache;
 
 public:
 
diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index 5f06bf009..d87825a6d 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -4611,9 +4611,9 @@ struct RegexCache
     }
 };
 
-std::shared_ptr<RegexCache> makeRegexCache()
+ref<RegexCache> makeRegexCache()
 {
-    return std::make_shared<RegexCache>();
+    return make_ref<RegexCache>();
 }
 
 void prim_match(EvalState & state, const PosIdx pos, Value ** args, Value & v)