diff --git a/app/javascript/mastodon/features/compose/components/compose_form.jsx b/app/javascript/mastodon/features/compose/components/compose_form.jsx
index 770f776049e..7f86f8fd84a 100644
--- a/app/javascript/mastodon/features/compose/components/compose_form.jsx
+++ b/app/javascript/mastodon/features/compose/components/compose_form.jsx
@@ -102,6 +102,7 @@ class ComposeForm extends ImmutablePureComponent {
   handleKeyDownPost = (e) => {
     if (e.key.toLowerCase() === 'enter' && (e.ctrlKey || e.metaKey)) {
         this.handleSubmit();
+        e.preventDefault();
     }
     this.blurOnEscape(e);
   };