diff --git a/src/components/views/rooms/MessageComposerInput.js b/src/components/views/rooms/MessageComposerInput.js
index 03ca16c72c..16551f8446 100644
--- a/src/components/views/rooms/MessageComposerInput.js
+++ b/src/components/views/rooms/MessageComposerInput.js
@@ -734,6 +734,7 @@ export default class MessageComposerInput extends React.Component {
             }[ev.keyCode];
 
             if (ctrlCmdCommand) {
+                ev.preventDefault(); // to prevent clashing with Mac's minimize window
                 return this.handleKeyCommand(ctrlCmdCommand);
             }
         }