diff --git a/res/css/views/rooms/_MessageComposerFormatBar.scss b/res/css/views/rooms/_MessageComposerFormatBar.scss
index 43a2fb257e..80909529ee 100644
--- a/res/css/views/rooms/_MessageComposerFormatBar.scss
+++ b/res/css/views/rooms/_MessageComposerFormatBar.scss
@@ -41,6 +41,18 @@ limitations under the License.
         &:hover {
             border-color: $message-action-bar-hover-border-color;
         }
+
+        &:first-child {
+            border-radius: 3px 0 0 3px;
+        }
+
+        &:last-child {
+            border-radius: 0 3px 3px 0;
+        }
+
+        &:only-child {
+            border-radius: 3px;
+        }
     }
 
     .mx_MessageComposerFormatBar_button {