diff --git a/src/libmain/shared.cc b/src/libmain/shared.cc
index a43a00f16..e09aed2c6 100644
--- a/src/libmain/shared.cc
+++ b/src/libmain/shared.cc
@@ -173,12 +173,13 @@ void initNix()
        everybody. */
     umask(0022);
 
-#ifndef _WIN32
     /* Initialise the PRNG. */
     struct timeval tv;
     gettimeofday(&tv, 0);
+#ifndef _WIN32
     srandom(tv.tv_usec);
 #endif
+    srand(tv.tv_usec);
 
 
 }
diff --git a/src/libstore/unix/gc.cc b/src/libstore/unix/gc.cc
index 9b2e6d525..68d049485 100644
--- a/src/libstore/unix/gc.cc
+++ b/src/libstore/unix/gc.cc
@@ -41,7 +41,7 @@ static void makeSymlink(const Path & link, const Path & target)
     createDirs(dirOf(link));
 
     /* Create the new symlink. */
-    Path tempLink = fmt("%1%.tmp-%2%-%3%", link, getpid(), random());
+    Path tempLink = fmt("%1%.tmp-%2%-%3%", link, getpid(), rand());
     createSymlink(target, tempLink);
 
     /* Atomically replace the old one. */