diff --git a/js/serial_backend.js b/js/serial_backend.js
index 5e40e8a4..6bb4b323 100755
--- a/js/serial_backend.js
+++ b/js/serial_backend.js
@@ -236,6 +236,9 @@ function onOpen(openInfo) {
         GUI.connecting_to = false;
 
         GUI.log(chrome.i18n.getMessage('serialPortOpened', [openInfo.connectionId]));
+        
+        // Reset the osdUnits
+        globalSettings.osdUnits = null;
 
         // save selected port with chrome.storage if the port differs
         chrome.storage.local.get('last_used_port', function (result) {