diff --git a/lix/libstore/build/derivation-goal.cc b/lix/libstore/build/derivation-goal.cc
index 892dde182..f88fde06e 100644
--- a/lix/libstore/build/derivation-goal.cc
+++ b/lix/libstore/build/derivation-goal.cc
@@ -769,7 +769,7 @@ void replaceValidPath(const Path & storePath, const Path & tmpPath)
     Path oldPath;
     if (pathExists(storePath)) {
         do {
-            oldPath = makeTempPath(storePath, ".old");
+            oldPath = makeTempSiblingPath(storePath);
             // store paths are often directories so we can't just unlink() it
             // let's make sure the path doesn't exist before we try to use it
         } while (pathExists(oldPath));