diff --git a/web/styles/compose.css b/web/styles/compose.css
index 6399d5ed0b..88d72d2fa8 100644
--- a/web/styles/compose.css
+++ b/web/styles/compose.css
@@ -540,10 +540,11 @@ input.recipient_box {
 }
 
 #stream_message_recipient_topic.recipient_box {
+    width: 100%;
     /* This width roughly corresponds to how long of a topic can appear in
        the left sidebar with a single digit unread count without being
        cut off. */
-    width: 175px;
+    max-width: 175px;
 }
 
 #private_message_recipient.recipient_box {