diff --git a/changelog.d/7497.bugfix b/changelog.d/7497.bugfix
new file mode 100644
index 0000000000..3c7920cb10
--- /dev/null
+++ b/changelog.d/7497.bugfix
@@ -0,0 +1 @@
+When sending `m.room.member` events, omit `displayname` and `avatar_url` if they aren't set instead of setting them to `null`. Contributed by Aaron Raimist.
diff --git a/synapse/handlers/message.py b/synapse/handlers/message.py
index 0242521cc6..8f362896a2 100644
--- a/synapse/handlers/message.py
+++ b/synapse/handlers/message.py
@@ -484,9 +484,13 @@ class EventCreationHandler(object):
 
                 try:
                     if "displayname" not in content:
-                        content["displayname"] = yield profile.get_displayname(target)
+                        displayname = yield profile.get_displayname(target)
+                        if displayname is not None:
+                            content["displayname"] = displayname
                     if "avatar_url" not in content:
-                        content["avatar_url"] = yield profile.get_avatar_url(target)
+                        avatar_url = yield profile.get_avatar_url(target)
+                        if avatar_url is not None:
+                            content["avatar_url"] = avatar_url
                 except Exception as e:
                     logger.info(
                         "Failed to get profile information for %r: %s", target, e