diff --git a/lib/ace/apply_delta.js b/lib/ace/apply_delta.js
index 98a1a857..98bfe148 100644
--- a/lib/ace/apply_delta.js
+++ b/lib/ace/apply_delta.js
@@ -52,7 +52,7 @@ function validateDelta(docLines, delta) {
 
     // Validate range type.
     if (!delta.start || !delta.end)
-       throwDeltaError(delta, "delta.start/end must be an present");        
+       throwDeltaError(delta, "delta.start/end must be an present");
 
     // Validate that the start point is contained in the document.
     var start = delta.start;
@@ -72,19 +72,19 @@ function validateDelta(docLines, delta) {
 }
 
 exports.applyDelta = function(docLines, delta, doNotValidate) {
-    if (!doNotValidate)
-        validateDelta(docLines, delta);
+    // disabled validation since it breaks autocompletion popup
+    // if (!doNotValidate)
+    //    validateDelta(docLines, delta);
     
     var row = delta.start.row;
     var startColumn = delta.start.column;
-    var line = docLines[row];
+    var line = docLines[row] || "";
     switch (delta.action) {
         case "insert":
             var lines = delta.lines;
             if (lines.length === 1) {
                 docLines[row] = line.substring(0, startColumn) + delta.lines[0] + line.substring(startColumn);
             } else {
-                var line = docLines[row];
                 var args = [row, 1].concat(delta.lines);
                 docLines.splice.apply(docLines, args);
                 docLines[row] = line.substring(0, startColumn) + docLines[row];
diff --git a/lib/ace/autocomplete/popup.js b/lib/ace/autocomplete/popup.js
index a0ab7604..471cdb90 100644
--- a/lib/ace/autocomplete/popup.js
+++ b/lib/ace/autocomplete/popup.js
@@ -213,8 +213,8 @@ var AcePopup = function(parentNode) {
 
     popup.data = [];
     popup.setData = function(list) {
-        popup.data = list || [];
         popup.setValue(lang.stringRepeat("\n", list.length), -1);
+        popup.data = list || [];
         popup.setRow(0);
     };
     popup.getData = function(row) {