--- a/mail/extensions/openpgp/content/ui/enigmailMsgComposeOverlay.js
+++ b/mail/extensions/openpgp/content/ui/enigmailMsgComposeOverlay.js
@@ -2832,17 +2832,17 @@ Enigmail.msg = {
     //}
 
     var exitCode = exitCodeObj.value;
 
     if (exitCode !== 0) {
       // Error processing
       var errorMsg = errorMsgObj.value;
 
-      var statusLines = errorMsg.split(/\r?\n/);
+      var statusLines = errorMsg ? errorMsg.split(/\r?\n/) : [];
 
       var displayMsg;
       if (statusLines && statusLines.length) {
         // Display only first ten lines of error message
         while (statusLines.length > 10) {
           statusLines.pop();
         }