1 files changed, 5 insertions, 6 deletions
diff --git a/synapse/config/_base.py b/synapse/config/_base.py
index 05a66841c3..85f65da4d9 100644
--- a/synapse/config/_base.py
+++ b/synapse/config/_base.py
@@ -242,12 +242,11 @@ class Config:
         env = jinja2.Environment(loader=loader, autoescape=autoescape)
 
         # Update the environment with our custom filters
-        env.filters.update(
-            {
-                "format_ts": _format_ts_filter,
-                "mxc_to_http": _create_mxc_to_http_filter(self.public_baseurl),
-            }
-        )
+        env.filters.update({"format_ts": _format_ts_filter})
+        if self.public_baseurl:
+            env.filters.update(
+                {"mxc_to_http": _create_mxc_to_http_filter(self.public_baseurl)}
+            )
 
         for filename in filenames:
             # Load the template