diff --git a/src/libutil/util.cc b/src/libutil/util.cc
index 1f923fe6bc0f..c36103f4a6b1 100644
--- a/src/libutil/util.cc
+++ b/src/libutil/util.cc
@@ -375,7 +375,7 @@ void deletePath(const Path & path, unsigned long long & bytesFreed)
 static Path tempName(Path tmpRoot, const Path & prefix, bool includePid,
     int & counter)
 {
-    tmpRoot = canonPath(tmpRoot.empty() ? getEnv("TMPDIR", "/tmp") : tmpRoot, true);
+    tmpRoot = canonPath(tmpRoot.empty() ? getEnv("NIX_TMPDIR", "/nix/var/tmp") : tmpRoot, true);
     if (includePid)
         return (format("%1%/%2%-%3%-%4%") % tmpRoot % prefix % getpid() % counter++).str();
     else