diff --git a/lib/ace/editor.js b/lib/ace/editor.js
index 3bdf1a08..97e78d36 100644
--- a/lib/ace/editor.js
+++ b/lib/ace/editor.js
@@ -50,8 +50,6 @@ var defaultCommands = require("./commands/default_commands").commands;
 var config = require("./config");
 
 /**
- *
- *
  * The main entry point into the Ace functionality.
  *
  * The `Editor` manages the [[EditSession]] (which manages [[Document]]s), as well as the [[VirtualRenderer]], which draws everything to the screen.
@@ -101,59 +99,40 @@ var Editor = function(renderer, session) {
     oop.implement(this, EventEmitter);
     
     this.$historyTracker = function(e) {
+        if (!this.$mergeUndoDeltas)
+            return;
+        var previous = this.previousCommand || {command:{}};
+        var mergeableCommands = ["backspace", "del", "insertstring"];
         if (e.command.name == "insertstring") {
             var text = e.args;
-            if (this.mergeNextCommand === undefined) {
+            if (this.mergeNextCommand === undefined)
                 this.mergeNextCommand = true;
-            }
-            var previousCommand = this.previousCommand || {};
-            if (
-                // previous command was the same
-                "insertstring" == previousCommand.name
-                // cursor was not moved since last command
-                && !this.cursorMoved
-                // previous command allows to coalesce with
-                && this.mergeNextCommand
-                // previous insertion was not a new line or a whitespace
-                // or this is a sequence of a new line or a whitespace insertions
-                && (!/ |\r\n|\r|\n/.test(text) || / |\r\n|\r|\n/.test(previousCommand.text))
-                // the sequence is not too long
-                && (new Date()) - this.sequenceStartTime < 2000
-                )
-                this.session.mergeUndoDeltas = true;
-            else
-                this.sequenceStartTime = new Date().getTime();
 
-            this.previousCommand = {
-                name: "insertstring",
-                text: text
-            }
-            this.cursorMoved = false;
+            var shouldMerge = e.command.name == previous.command.name // previous command was the same
+                && !this.cursorMoved // cursor was not moved since last command
+                && this.mergeNextCommand // previous command allows to coalesce with
+                && (!/\s/.test(text) || /\s/.test(previous.args)) // previous insertion was of same type
+
             this.mergeNextCommand = true;
         } else {
-            var mergeableCommands = ["backspace", "del"];
-            var previousCommand = this.previousCommand || {};
-            if (
-                // previous command was the same
-                e.command.name == previousCommand.name
-                // the command is mergeable
-                && mergeableCommands.indexOf(e.command.name) !== -1
-                // cursor was not moved since last command
-                && !this.cursorMoved
-                // the sequence is not too long
-                && (new Date()) - this.sequenceStartTime < 2000
-                )
-                this.session.mergeUndoDeltas = true
-            else
-                if (mergeableCommands.indexOf(e.command.name) !== -1)
-                    this.sequenceStartTime = new Date().getTime();
-
-            this.previousCommand = {
-                name: e.command.name,
-                text: e.command.text
-            }
-            this.cursorMoved = false;
+            var shouldMerge = e.command.name == previous.command.name // previous command was the same
+                && mergeableCommands.indexOf(e.command.name) !== -1// the command is mergeable
+                && !this.cursorMoved // cursor was not moved since last command
         }
+        
+        if (
+            this.$mergeUndoDeltas != "always"
+            && Date.now() - this.sequenceStartTime < 2000
+        ) {
+            shouldMerge = false; // the sequence is too long
+        }
+        
+        if (shouldMerge)
+            this.session.mergeUndoDeltas = true;
+        else if (mergeableCommands.indexOf(e.command.name) !== -1)
+            this.sequenceStartTime = Date.now();
+        this.cursorMoved = false;
+        this.previousCommand = e;
     };
 
     /**
@@ -2308,6 +2287,10 @@ config.defineOptions(Editor.prototype, "editor", {
         values: ["ace", "slim", "smooth", "wide"],
         initialValue: "ace"
     },
+    mergeUndoDeltas: {
+        values: [false, true, "always"],
+        initialValue: false
+    },
     behavioursEnabled: {initialValue: true},
     wrapBehavioursEnabled: {initialValue: true},