diff --git a/lib/ace/autocomplete.js b/lib/ace/autocomplete.js
index 1277fe33..9f7e6ad0 100644
--- a/lib/ace/autocomplete.js
+++ b/lib/ace/autocomplete.js
@@ -226,7 +226,7 @@ var Autocomplete = function() {
     this.updateCompletions = function(keepPopupPosition) {
         if (keepPopupPosition && this.base && this.completions) {
             var pos = this.editor.getCursorPosition();
-            var prefix = ace.session.getTextRange({start: this.base, end: pos});
+            var prefix = this.editor.session.getTextRange({start: this.base, end: pos});
             if (prefix == this.completions.filterText)
                 return;
             this.completions.setFilter(prefix);