diff --git a/lib/ace/edit_session.js b/lib/ace/edit_session.js
index 6c33c449..6ccb6a91 100644
--- a/lib/ace/edit_session.js
+++ b/lib/ace/edit_session.js
@@ -348,16 +348,16 @@ var EditSession = function(text, mode) {
     this.setUseWorker = function(useWorker) {
         if (this.$useWorker == useWorker)
             return;
-            
+
         if (useWorker && !this.$worker && window.Worker)
             this.$worker = mode.createWorker(this);
-            
+
         if (!useWorker && this.$worker) {
             this.$worker.terminate();
             this.$worker = null;
         }
     };
-    
+
     this.getUseWorker = function() {
         return this.$useWorker;
     };
@@ -417,14 +417,11 @@ var EditSession = function(text, mode) {
             var tabSize = this.getTabSize();
 
             for ( var i = 0; i < lines.length; i++) {
-                var len = lines[i].length;
+                var line = lines[i],
+                    len = line.length,
+                    screenLen = this.$getStringScreenWidth(line);
                 longestLine = Math.max(longestLine, len);
-
-                lines[i].replace(/\t/g, function(m) {
-                    len += tabSize-1;
-                    return m;
-                });
-                longestScreenLine = Math.max(longestScreenLine, len);
+                longestScreenLine = Math.max(longestScreenLine, screenLen);
             }
             this.width = longestLine;
 
@@ -601,7 +598,7 @@ var EditSession = function(text, mode) {
 
 
         var actions = [{}];
-        
+
         // collapse insert and remove operations
         for (var i=0; i<deltas.length; i++) {
             var delta = deltas[i];
@@ -615,7 +612,7 @@ var EditSession = function(text, mode) {
                 })
             }
             else {
-                if (isInsert)    
+                if (isInsert)
                     action.end = delta.range.end;
                 else
                     action.start = delta.range.start;
@@ -625,12 +622,12 @@ var EditSession = function(text, mode) {
         // update selection based on last operation
         this.selection.clearSelection();
         var action = actions[actions.length-1];
-        if (action.isInsert) 
+        if (action.isInsert)
             this.selection.setSelectionRange(Range.fromPoints(action.start, action.end));
-        else 
+        else
             this.selection.moveCursorToPosition(action.end);
     },
-    
+
     this.replace = function(range, text) {
         return this.doc.replace(range, text);
     };
@@ -988,7 +985,7 @@ var EditSession = function(text, mode) {
     this.$getStringScreenWidth = function(str) {
         var screenColumn = 0;
         var tabSize = this.getTabSize();
-		
+
 		for (var i=0; i<str.length; i++) {
 			var c = str.charCodeAt(i);
 			// tab
@@ -1008,7 +1005,7 @@ var EditSession = function(text, mode) {
 				screenColumn += 1;
 			}
 		}
-		
+
 		return screenColumn;
     }