diff --git a/src/components/views/dialogs/CreateGroupDialog.js b/src/components/views/dialogs/CreateGroupDialog.js
index ccb051d3e1..a0b8f84130 100644
--- a/src/components/views/dialogs/CreateGroupDialog.js
+++ b/src/components/views/dialogs/CreateGroupDialog.js
@@ -66,8 +66,12 @@ export default React.createClass({
                 {domain: MatrixClientPeg.get().getDomain()},
             );
         } else {
+            const groupId = parsedGroupId[0];
             const domain = parsedGroupId[1];
-            if (domain !== MatrixClientPeg.get().getDomain()) {
+
+            if (!/^[a-zA-Z0-9]*$/.test(groupId)) {
+                error = _t("Community IDs may only contain alphanumeric characters");
+            } else if (domain !== MatrixClientPeg.get().getDomain()) {
                 error = _t(
                     "It is currently only possible to create communities on your own home server: "+
                     "use a community ID ending with %(domain)s",
diff --git a/src/i18n/strings/en_EN.json b/src/i18n/strings/en_EN.json
index 9fbf16e5da..3b48ebefaa 100644
--- a/src/i18n/strings/en_EN.json
+++ b/src/i18n/strings/en_EN.json
@@ -583,6 +583,7 @@
     "Are you sure you wish to remove (delete) this event? Note that if you delete a room name or topic change, it could undo the change.": "Are you sure you wish to remove (delete) this event? Note that if you delete a room name or topic change, it could undo the change.",
     "%(actionVerb)s this person?": "%(actionVerb)s this person?",
     "Community IDs must be of the form +localpart:%(domain)s": "Community IDs must be of the form +localpart:%(domain)s",
+    "Community IDs may only contain alphanumeric characters": "Community IDs may only contain alphanumeric characters",
     "It is currently only possible to create communities on your own home server: use a community ID ending with %(domain)s": "It is currently only possible to create communities on your own home server: use a community ID ending with %(domain)s",
     "Room creation failed": "Room creation failed",
     "Create Community": "Create Community",