diff --git a/chrome/content/zotero/xpcom/utilities.js b/chrome/content/zotero/xpcom/utilities.js
index 064e4f2b7..fd7ec0684 100644
--- a/chrome/content/zotero/xpcom/utilities.js
+++ b/chrome/content/zotero/xpcom/utilities.js
@@ -903,6 +903,7 @@ Zotero.Utilities.HTTP = new function() {
 		xmlhttp.onreadystatechange = function() {
 			_stateChange(xmlhttp, callback);
 		};
+		xmlhttp.overrideMimeType("text/plain");
 		xmlhttp.send(null);
 		return xmlhttp;
 	}