diff --git a/src/libstore/build.cc b/src/libstore/build.cc
index d1c9f1727..6def0c1c5 100644
--- a/src/libstore/build.cc
+++ b/src/libstore/build.cc
@@ -368,8 +368,6 @@ void commonChildInit(Pipe & logPipe)
     /* Dup the write side of the logger pipe into stderr. */
     if (dup2(logPipe.writeSide, STDERR_FILENO) == -1)
         throw SysError("cannot pipe standard error into log file");
-    logPipe.readSide.close();
-    logPipe.writeSide.close();
 
     /* Dup stderr to stdout. */
     if (dup2(STDERR_FILENO, STDOUT_FILENO) == -1)
@@ -681,12 +679,10 @@ HookInstance::HookInstance()
             if (chdir("/") == -1) throw SysError("changing into `/");
 
             /* Dup the communication pipes. */
-            toHook.writeSide.close();
             if (dup2(toHook.readSide, STDIN_FILENO) == -1)
                 throw SysError("dupping to-hook read side");
 
             /* Use fd 4 for the builder's stdout/stderr. */
-            builderOut.readSide.close();
             if (dup2(builderOut.writeSide, 4) == -1)
                 throw SysError("dupping builder's stdout/stderr");
 
@@ -2680,8 +2676,6 @@ void SubstitutionGoal::tryToRun()
 
             if (dup2(outPipe.writeSide, STDOUT_FILENO) == -1)
                 throw SysError("cannot dup output pipe into stdout");
-            outPipe.readSide.close();
-            outPipe.writeSide.close();
 
             /* Pass configuration options (including those overriden
                with --option) to the substituter. */
diff --git a/src/libstore/local-store.cc b/src/libstore/local-store.cc
index bcf367d65..d6cdd10d6 100644
--- a/src/libstore/local-store.cc
+++ b/src/libstore/local-store.cc
@@ -968,8 +968,6 @@ void LocalStore::startSubstituter(const Path & substituter, RunningSubstituter &
                with --option) to the substituter. */
             setenv("_NIX_OPTIONS", settings.pack().c_str(), 1);
 
-            fromPipe.readSide.close();
-            toPipe.writeSide.close();
             if (dup2(toPipe.readSide, STDIN_FILENO) == -1)
                 throw SysError("dupping stdin");
             if (dup2(fromPipe.writeSide, STDOUT_FILENO) == -1)
diff --git a/src/libutil/util.cc b/src/libutil/util.cc
index bfed96846..7e5d8bb80 100644
--- a/src/libutil/util.cc
+++ b/src/libutil/util.cc
@@ -870,7 +870,13 @@ void killUser(uid_t uid)
 string runProgram(Path program, bool searchPath, const Strings & args)
 {
     checkInterrupt();
-    
+
+    std::vector<const char *> cargs; /* careful with c_str()! */
+    cargs.push_back(program.c_str());
+    for (Strings::const_iterator i = args.begin(); i != args.end(); ++i)
+        cargs.push_back(i->c_str());
+    cargs.push_back(0);
+
     /* Create a pipe. */
     Pipe pipe;
     pipe.create();
@@ -885,23 +891,15 @@ string runProgram(Path program, bool searchPath, const Strings & args)
 
     case 0: /* child */
         try {
-            pipe.readSide.close();
-
             if (dup2(pipe.writeSide, STDOUT_FILENO) == -1)
                 throw SysError("dupping stdout");
 
-            std::vector<const char *> cargs; /* careful with c_str()! */
-            cargs.push_back(program.c_str());
-            for (Strings::const_iterator i = args.begin(); i != args.end(); ++i)
-                cargs.push_back(i->c_str());
-            cargs.push_back(0);
-
             if (searchPath)
                 execvp(program.c_str(), (char * *) &cargs[0]);
             else
                 execv(program.c_str(), (char * *) &cargs[0]);
             throw SysError(format("executing `%1%'") % program);
-            
+
         } catch (std::exception & e) {
             std::cerr << "error: " << e.what() << std::endl;
         }