diff --git a/app/javascript/flavours/glitch/features/compose/components/compose_form.jsx b/app/javascript/flavours/glitch/features/compose/components/compose_form.jsx
index 20f5a1fb92..be645147db 100644
--- a/app/javascript/flavours/glitch/features/compose/components/compose_form.jsx
+++ b/app/javascript/flavours/glitch/features/compose/components/compose_form.jsx
@@ -110,10 +110,12 @@ class ComposeForm extends ImmutablePureComponent {
   handleKeyDownPost = (e) => {
     if (e.key.toLowerCase() === 'enter' && (e.ctrlKey || e.metaKey)) {
       this.handleSubmit(e);
+      e.preventDefault();
     }
 
     if (e.key.toLowerCase() === 'enter' && e.altKey) {
       this.handleSecondarySubmit(e);
+      e.preventDefault();
     }
 
     this.blurOnEscape(e);