diff --git a/tests/run-tests.py b/tests/run-tests.py
--- a/tests/run-tests.py
+++ b/tests/run-tests.py
@@ -1068,6 +1068,7 @@
         env["HGUSER"]   = "test"
         env["HGENCODING"] = "ascii"
         env["HGENCODINGMODE"] = "strict"
+        env["HGHOSTNAME"] = "test-hostname"
         env['HGIPV6'] = str(int(self._useipv6))
 
         extraextensions = []