diff --git a/rest_framework/static/rest_framework/js/ajax-form.js b/rest_framework/static/rest_framework/js/ajax-form.js
index fc00926f5..1483305ff 100644
--- a/rest_framework/static/rest_framework/js/ajax-form.js
+++ b/rest_framework/static/rest_framework/js/ajax-form.js
@@ -42,7 +42,7 @@ function doAjaxSubmit(e) {
       // We need to add a boundary parameter to the header
       // We assume the first valid-looking boundary line in the body is correct
       // regex is from RFC 2046 appendix A
-      var boundaryCharNoSpace = "[0-9A-Z'()+_,-./:=?";
+      var boundaryCharNoSpace = "0-9A-Z'()+_,-./:=?";
       var boundaryChar = boundaryCharNoSpace + ' ';
       var re = new RegExp('^--([' + boundaryChar + ']{0,69}[' + boundaryCharNoSpace + '])[\\s]*?$', 'im');
       var boundary = data.match(re);