diff --git a/src/libstore/include/nix/store/build/derivation-building-goal.hh b/src/libstore/include/nix/store/build/derivation-building-goal.hh
index f6dcad83d..2cb111760 100644
--- a/src/libstore/include/nix/store/build/derivation-building-goal.hh
+++ b/src/libstore/include/nix/store/build/derivation-building-goal.hh
@@ -29,6 +29,12 @@ typedef enum { rpAccept, rpDecline, rpPostpone } HookReply;
  */
 struct DerivationBuildingGoal : public Goal
 {
+    DerivationBuildingGoal(
+        const StorePath & drvPath, const Derivation & drv, Worker & worker, BuildMode buildMode = bmNormal);
+    ~DerivationBuildingGoal();
+
+private:
+
     /** The path of the derivation. */
     StorePath drvPath;
 
@@ -94,10 +100,6 @@ struct DerivationBuildingGoal : public Goal
      */
     std::string machineName;
 
-    DerivationBuildingGoal(
-        const StorePath & drvPath, const Derivation & drv, Worker & worker, BuildMode buildMode = bmNormal);
-    ~DerivationBuildingGoal();
-
     void timedOut(Error && ex) override;
 
     std::string key() override;