diff --git a/src/libstore/build/goal.cc b/src/libstore/build/goal.cc
index 2dd7a4d37..9de40bdf2 100644
--- a/src/libstore/build/goal.cc
+++ b/src/libstore/build/goal.cc
@@ -78,6 +78,8 @@ void Goal::amDone(ExitCode result, std::optional<Error> ex)
     }
     waiters.clear();
     worker.removeGoal(shared_from_this());
+
+    cleanup();
 }
 
 
diff --git a/src/libstore/build/goal.hh b/src/libstore/build/goal.hh
index fca4f2d00..e6bf628cb 100644
--- a/src/libstore/build/goal.hh
+++ b/src/libstore/build/goal.hh
@@ -100,6 +100,8 @@ struct Goal : public std::enable_shared_from_this<Goal>
     virtual string key() = 0;
 
     void amDone(ExitCode result, std::optional<Error> ex = {});
+
+    virtual void cleanup() { }
 };
 
 void addToWeakGoals(WeakGoals & goals, GoalPtr p);
diff --git a/src/libstore/build/substitution-goal.cc b/src/libstore/build/substitution-goal.cc
index 7b1ac126e..e56cfadbe 100644
--- a/src/libstore/build/substitution-goal.cc
+++ b/src/libstore/build/substitution-goal.cc
@@ -20,15 +20,7 @@ PathSubstitutionGoal::PathSubstitutionGoal(const StorePath & storePath, Worker &
 
 PathSubstitutionGoal::~PathSubstitutionGoal()
 {
-    try {
-        if (thr.joinable()) {
-            // FIXME: signal worker thread to quit.
-            thr.join();
-            worker.childTerminated(this);
-        }
-    } catch (...) {
-        ignoreException();
-    }
+    cleanup();
 }
 
 
@@ -63,6 +55,8 @@ void PathSubstitutionGoal::tryNext()
 {
     trace("trying next substituter");
 
+    cleanup();
+
     if (subs.size() == 0) {
         /* None left.  Terminate this goal and let someone else deal
            with it. */
@@ -205,7 +199,7 @@ void PathSubstitutionGoal::tryToRun()
     thr = std::thread([this]() {
         try {
             /* Wake up the worker loop when we're done. */
-            Finally updateStats([this]() { outPipe.writeSide = -1; });
+            Finally updateStats([this]() { outPipe.writeSide.close(); });
 
             Activity act(*logger, actSubstitute, Logger::Fields{worker.store.printStorePath(storePath), sub->getUri()});
             PushActivity pact(act.id);
@@ -288,4 +282,21 @@ void PathSubstitutionGoal::handleEOF(int fd)
     if (fd == outPipe.readSide.get()) worker.wakeUp(shared_from_this());
 }
 
+
+void PathSubstitutionGoal::cleanup()
+{
+    try {
+        if (thr.joinable()) {
+            // FIXME: signal worker thread to quit.
+            thr.join();
+            worker.childTerminated(this);
+        }
+
+        outPipe.close();
+    } catch (...) {
+        ignoreException();
+    }
+}
+
+
 }
diff --git a/src/libstore/build/substitution-goal.hh b/src/libstore/build/substitution-goal.hh
index 3b3cb7e32..70c806d23 100644
--- a/src/libstore/build/substitution-goal.hh
+++ b/src/libstore/build/substitution-goal.hh
@@ -14,7 +14,7 @@ struct PathSubstitutionGoal : public Goal
     StorePath storePath;
 
     /* The path the substituter refers to the path as. This will be
-     * different when the stores have different names. */
+       different when the stores have different names. */
     std::optional<StorePath> subPath;
 
     /* The remaining substituters. */
@@ -79,6 +79,8 @@ public:
     /* Callback used by the worker to write to the log. */
     void handleChildOutput(int fd, const string & data) override;
     void handleEOF(int fd) override;
+
+    void cleanup() override;
 };
 
 }
diff --git a/src/libstore/build/worker.cc b/src/libstore/build/worker.cc
index 6c04d3ed3..0f2ade348 100644
--- a/src/libstore/build/worker.cc
+++ b/src/libstore/build/worker.cc
@@ -128,6 +128,7 @@ void Worker::removeGoal(GoalPtr goal)
         nix::removeGoal(subGoal, drvOutputSubstitutionGoals);
     else
         assert(false);
+
     if (topGoals.find(goal) != topGoals.end()) {
         topGoals.erase(goal);
         /* If a top-level goal failed, then kill all other goals
diff --git a/src/libutil/util.cc b/src/libutil/util.cc
index dea9c74b7..a6fcabbec 100644
--- a/src/libutil/util.cc
+++ b/src/libutil/util.cc
@@ -752,13 +752,13 @@ AutoCloseFD::AutoCloseFD() : fd{-1} {}
 AutoCloseFD::AutoCloseFD(int fd) : fd{fd} {}
 
 
-AutoCloseFD::AutoCloseFD(AutoCloseFD&& that) : fd{that.fd}
+AutoCloseFD::AutoCloseFD(AutoCloseFD && that) : fd{that.fd}
 {
     that.fd = -1;
 }
 
 
-AutoCloseFD& AutoCloseFD::operator =(AutoCloseFD&& that)
+AutoCloseFD & AutoCloseFD::operator =(AutoCloseFD && that)
 {
     close();
     fd = that.fd;
@@ -789,6 +789,7 @@ void AutoCloseFD::close()
         if (::close(fd) == -1)
             /* This should never happen. */
             throw SysError("closing file descriptor %1%", fd);
+        fd = -1;
     }
 }
 
@@ -822,6 +823,12 @@ void Pipe::create()
 }
 
 
+void Pipe::close()
+{
+    readSide.close();
+    writeSide.close();
+}
+
 
 //////////////////////////////////////////////////////////////////////
 
@@ -1121,7 +1128,7 @@ void runProgram2(const RunOptions & options)
         throw SysError("executing '%1%'", options.program);
     }, processOptions);
 
-    out.writeSide = -1;
+    out.writeSide.close();
 
     std::thread writerThread;
 
@@ -1134,7 +1141,7 @@ void runProgram2(const RunOptions & options)
 
 
     if (source) {
-        in.readSide = -1;
+        in.readSide.close();
         writerThread = std::thread([&]() {
             try {
                 std::vector<char> buf(8 * 1024);
@@ -1151,7 +1158,7 @@ void runProgram2(const RunOptions & options)
             } catch (...) {
                 promise.set_exception(std::current_exception());
             }
-            in.writeSide = -1;
+            in.writeSide.close();
         });
     }
 
diff --git a/src/libutil/util.hh b/src/libutil/util.hh
index ad49c65b3..ef5e5012b 100644
--- a/src/libutil/util.hh
+++ b/src/libutil/util.hh
@@ -188,7 +188,6 @@ public:
 class AutoCloseFD
 {
     int fd;
-    void close();
 public:
     AutoCloseFD();
     AutoCloseFD(int fd);
@@ -200,6 +199,7 @@ public:
     int get() const;
     explicit operator bool() const;
     int release();
+    void close();
 };
 
 
@@ -216,6 +216,7 @@ class Pipe
 public:
     AutoCloseFD readSide, writeSide;
     void create();
+    void close();
 };