diff --git a/lib/ace/mode/ruby_highlight_rules.js b/lib/ace/mode/ruby_highlight_rules.js
index 2d980bb1..8de4d903 100644
--- a/lib/ace/mode/ruby_highlight_rules.js
+++ b/lib/ace/mode/ruby_highlight_rules.js
@@ -131,7 +131,7 @@ var RubyHighlightRules = function() {
 	            regex : "0[xX][0-9a-fA-F]+\\b"
 	        }, {
 	            token : "constant.numeric", // float
-	            regex : "[+-]?\\d+(?:(?:\\.\\d*)?(?:[eE][+-]?\\d+)?)?\\b"
+	            regex : "[+-]?\\d(?:\\d|_(?=\\d))*(?:(?:\\.\\d(?:\\d|_(?=\\d))*)?(?:[eE][+-]?\\d+)?)?\\b"
 	        }, {
 	            token : "constant.language.boolean",
 	            regex : "(?:true|false)\\b"
diff --git a/lib/ace/mode/ruby_tokenizer_test.js b/lib/ace/mode/ruby_tokenizer_test.js
index 9127b954..37f4e2a3 100644
--- a/lib/ace/mode/ruby_tokenizer_test.js
+++ b/lib/ace/mode/ruby_tokenizer_test.js
@@ -59,6 +59,13 @@ module.exports = {
         assertInvalidTokens(this.tokenizer, "string",
           [":", ":@", ":$", ":1", ":1thing", ":th?ing", ":thi=ng", ":1thing",
             ":th!ing", ":thing#"]);
+    },
+
+    "test: float tokenizer" : function() {
+        assertValidTokens(this.tokenizer, "constant.numeric",
+            ["1", "+1", "-1", "12_345", "0.000_1"]);
+        assertInvalidTokens(this.tokenizer, "constant.numeric",
+            ["_", "_1", "1_", "1_.0", "0._1"]);
     }
 };