diff --git a/src/shared/components/home/signup.tsx b/src/shared/components/home/signup.tsx
index ebccac98..c3fcd20e 100644
--- a/src/shared/components/home/signup.tsx
+++ b/src/shared/components/home/signup.tsx
@@ -144,7 +144,7 @@ export class Signup extends Component<any, State> {
               onInput={linkEvent(this, this.handleRegisterUsernameChange)}
               required
               minLength={3}
-              pattern="[a-zA-Z0-9_]+"
+              pattern="[a-z0-9_]+"
               title={i18n.t("community_reqs")}
             />
           </div>