diff --git a/tests/unit/libstore-support/tests/libstore.hh b/tests/unit/libstore-support/tests/libstore.hh
index ef93457b5..75093d3cd 100644
--- a/tests/unit/libstore-support/tests/libstore.hh
+++ b/tests/unit/libstore-support/tests/libstore.hh
@@ -4,6 +4,7 @@
 #include <gtest/gtest.h>
 #include <gmock/gmock.h>
 
+#include "globals.hh"
 #include "store-api.hh"
 
 namespace nix {
@@ -11,6 +12,7 @@ namespace nix {
 class LibStoreTest : public ::testing::Test {
     public:
         static void SetUpTestSuite() {
+            settings.nixConfDir = "/dev/null"; // intentionally invalid path
             initLibStore();
         }