diff --git a/tests/http/__init__.py b/tests/http/__init__.py
index 126826fd3..2d5dba646 100644
--- a/tests/http/__init__.py
+++ b/tests/http/__init__.py
@@ -50,7 +50,7 @@ CONFIG_TEMPLATE = b"""\
 [default]
 basicConstraints = CA:FALSE
 keyUsage=nonRepudiation, digitalSignature, keyEncipherment
-subjectAltName = %(sanentries)b
+subjectAltName = %(sanentries)s
 """