diff --git a/src/libmain/progress-bar.cc b/src/libmain/progress-bar.cc
index 6600ec177..45b1fdfd1 100644
--- a/src/libmain/progress-bar.cc
+++ b/src/libmain/progress-bar.cc
@@ -108,7 +108,8 @@ public:
         stop();
     }
 
-    void stop() override
+    /* Called by destructor, can't be overridden */
+    void stop() override final
     {
         {
             auto state(state_.lock());
diff --git a/src/libstore/build/local-derivation-goal.hh b/src/libstore/build/local-derivation-goal.hh
index 9acd7593d..8827bfca3 100644
--- a/src/libstore/build/local-derivation-goal.hh
+++ b/src/libstore/build/local-derivation-goal.hh
@@ -272,8 +272,10 @@ struct LocalDerivationGoal : public DerivationGoal
 
     /**
      * Forcibly kill the child process, if any.
+     *
+     * Called by destructor, can't be overridden
      */
-    void killChild() override;
+    void killChild() override final;
 
     /**
      * Kill any processes running under the build user UID or in the
diff --git a/src/libstore/build/substitution-goal.hh b/src/libstore/build/substitution-goal.hh
index 9fc041920..1b693baa1 100644
--- a/src/libstore/build/substitution-goal.hh
+++ b/src/libstore/build/substitution-goal.hh
@@ -114,7 +114,8 @@ public:
     void handleChildOutput(int fd, std::string_view data) override;
     void handleEOF(int fd) override;
 
-    void cleanup() override;
+    /* Called by destructor, can't be overridden */
+    void cleanup() override final;
 
     JobCategory jobCategory() override { return JobCategory::Substitution; };
 };