diff --git a/changelog.d/4564.bugfix b/changelog.d/4564.bugfix
new file mode 100644
index 0000000000..78e78504b4
--- /dev/null
+++ b/changelog.d/4564.bugfix
@@ -0,0 +1 @@
+Fix default ACME config for py2
diff --git a/synapse/config/tls.py b/synapse/config/tls.py
index 9498fc5f5b..b5f2cfd9b7 100644
--- a/synapse/config/tls.py
+++ b/synapse/config/tls.py
@@ -37,7 +37,7 @@ class TlsConfig(Config):
 
         self.acme_enabled = acme_config.get("enabled", False)
         self.acme_url = acme_config.get(
-            "url", "https://acme-v01.api.letsencrypt.org/directory"
+            "url", u"https://acme-v01.api.letsencrypt.org/directory"
         )
         self.acme_port = acme_config.get("port", 80)
         self.acme_bind_addresses = acme_config.get("bind_addresses", ['::', '0.0.0.0'])