diff --git a/changelog.d/18593.bugfix b/changelog.d/18593.bugfix
new file mode 100644
index 0000000000..9079b9534a
--- /dev/null
+++ b/changelog.d/18593.bugfix
@@ -0,0 +1 @@
+Fix `avatar_url` and `displayname` being sent on federation profile queries when they are not set.
\ No newline at end of file
diff --git a/synapse/handlers/profile.py b/synapse/handlers/profile.py
index cdc388b4ab..76aa90e11b 100644
--- a/synapse/handlers/profile.py
+++ b/synapse/handlers/profile.py
@@ -539,11 +539,17 @@ class ProfileHandler:
         response: JsonDict = {}
         try:
             if just_field is None or just_field == ProfileFields.DISPLAYNAME:
-                response["displayname"] = await self.store.get_profile_displayname(user)
-
+                displayname = await self.store.get_profile_displayname(user)
+                # do not set the displayname field if it is None,
+                # since then we send a null in the JSON response
+                if displayname is not None:
+                    response["displayname"] = displayname
             if just_field is None or just_field == ProfileFields.AVATAR_URL:
-                response["avatar_url"] = await self.store.get_profile_avatar_url(user)
-
+                avatar_url = await self.store.get_profile_avatar_url(user)
+                # do not set the avatar_url field if it is None,
+                # since then we send a null in the JSON response
+                if avatar_url is not None:
+                    response["avatar_url"] = avatar_url
             if self.hs.config.experimental.msc4133_enabled:
                 if just_field is None:
                     response.update(await self.store.get_profile_fields(user))