diff --git a/changelog.d/10779.misc b/changelog.d/10779.misc
new file mode 100644
index 0000000000..9275a83039
--- /dev/null
+++ b/changelog.d/10779.misc
@@ -0,0 +1 @@
+Change the format of authenticated users in logs when a user is being puppeted by and admin user.
diff --git a/synapse/http/site.py b/synapse/http/site.py
index 190084e8aa..c665a9d5db 100644
--- a/synapse/http/site.py
+++ b/synapse/http/site.py
@@ -384,7 +384,7 @@ class SynapseRequest(Request):
         # authenticated (e.g. and admin is puppetting a user) then we log both.
         requester, authenticated_entity = self.get_authenticated_entity()
         if authenticated_entity:
-            requester = f"{authenticated_entity}.{requester}"
+            requester = f"{authenticated_entity}|{requester}"
 
         self.site.access_logger.log(
             log_level,