diff --git a/master/custom/factories.py b/master/custom/factories.py
index a45f23b1..b26bb643 100644
--- a/master/custom/factories.py
+++ b/master/custom/factories.py
@@ -893,7 +893,10 @@ def setup(self, parallel, branch, test_with_PTY=False, **kwargs):
                 warnOnFailure=True,
             )
         )
-        self.host_configure_cmd.append(util.Interpolate("CONFIG_SITE=%(prop:config_site)s"))
+        self.compile_environ = super().compile_environ.copy()
+        self.compile_environ.update(
+            CONFIG_SITE=util.Interpolate("../../%(prop:config_site)s")
+        )
         self.addStep(
             ShellCommand(
                 name="Touch srcdir Modules/Setup.local",