diff --git a/lib/ace/mode/markdown_highlight_rules.js b/lib/ace/mode/markdown_highlight_rules.js
index 276d77cc..4fbc3918 100644
--- a/lib/ace/mode/markdown_highlight_rules.js
+++ b/lib/ace/mode/markdown_highlight_rules.js
@@ -69,9 +69,9 @@ var MarkdownHighlightRules = function() {
             regex: "^\\-+(?=\\s*$)"
         }, { // header
             token : function(value) {
-                return "markup.heading." + value.length;
+                return "markup.heading." + value.search(/[^#]/);
             },
-            regex : "^#{1,6}"
+            regex : "^#{1,6}(?:[^ #].*| +.*(?:[^ #].*|[^ ]+.* +#+ *))$"
         }, github_embed("(?:javascript|js)", "js-"),
            github_embed("xml", "xml-"),
            github_embed("html", "html-"),
diff --git a/lib/ace/mode/markdown_highlight_rules_test.js b/lib/ace/mode/markdown_highlight_rules_test.js
new file mode 100644
index 00000000..4c828e49
--- /dev/null
+++ b/lib/ace/mode/markdown_highlight_rules_test.js
@@ -0,0 +1,100 @@
+/* ***** BEGIN LICENSE BLOCK *****
+ * Distributed under the BSD license:
+ *
+ * Copyright (c) 2012, Ajax.org B.V.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *     * Redistributions of source code must retain the above copyright
+ *       notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above copyright
+ *       notice, this list of conditions and the following disclaimer in the
+ *       documentation and/or other materials provided with the distribution.
+ *     * Neither the name of Ajax.org B.V. nor the
+ *       names of its contributors may be used to endorse or promote products
+ *       derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL AJAX.ORG B.V. BE LIABLE FOR ANY
+ * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ *
+ * Contributor(s):
+ *
+ * quexer <quexer AT gmail DOT com>
+ *
+ * ***** END LICENSE BLOCK ***** */
+
+if (typeof process !== "undefined") {
+    require("amd-loader");
+}
+
+define(function(require, exports, module) {
+"use strict";
+
+var Mode = require("./markdown").Mode;
+var assert = require("../test/assertions");
+
+module.exports = {
+    setUp : function() {
+        this.tokenizer = new Mode().getTokenizer();
+    },
+
+    "test: header 1 ": function() {
+        var tokens = this.tokenizer.getLineTokens("#f", "start").tokens;
+        assert.equal(tokens.length, 1);
+        assert.equal(tokens[0].type, 'markup.heading.1');
+    },
+
+    "test: header 2": function() {
+        var tokens = this.tokenizer.getLineTokens("## foo", "start").tokens;
+        assert.equal(tokens.length, 1);
+        assert.equal(tokens[0].type, 'markup.heading.2');
+    },
+
+    "test: header ends with ' #'": function() {
+        var tokens = this.tokenizer.getLineTokens("# # # ", "start").tokens;
+        assert.equal(tokens.length, 1);
+        assert.equal(tokens[0].type, 'markup.heading.1');
+    },
+
+    "test: header ends with '#'": function() {
+        var tokens = this.tokenizer.getLineTokens("#foo# ", "start").tokens;
+        assert.equal(tokens.length, 1);
+        assert.equal(tokens[0].type, 'markup.heading.1');
+    },
+
+    "test: 6+ #s is not a valid header": function() {
+        var tokens = this.tokenizer.getLineTokens("####### foo", "start").tokens;
+        assert.equal(tokens.length, 1);
+        assert.equal(tokens[0].type, 'text');
+    },
+
+    "test: # followed be only space is not a valid header": function() {
+        var tokens = this.tokenizer.getLineTokens("#  ", "start").tokens;
+        assert.equal(tokens.length, 1);
+        assert.equal(tokens[0].type, 'text');
+    },
+
+
+
+    "test: only space between #s is not a valid header": function() {
+        var tokens = this.tokenizer.getLineTokens("#  #", "start").tokens;
+        assert.equal(tokens.length, 1);
+        assert.equal(tokens[0].type, 'text');
+    }
+};
+
+});
+
+if (typeof module !== "undefined" && module === require.main) {
+    require("asyncjs").test.testcase(module.exports).exec();
+}