diff --git a/lib/coffee-script/nodes.js b/lib/coffee-script/nodes.js
index 37807c5fe2..bbf7adf22e 100644
--- a/lib/coffee-script/nodes.js
+++ b/lib/coffee-script/nodes.js
@@ -3073,7 +3073,7 @@
       return "[].indexOf || function(item) { for (var i = 0, l = this.length; i < l; i++) { if (i in this && this[i] === item) return i; } return -1; }";
     },
     modulo: function() {
-      return "function(a, b) { return (a % b + b) % b; }";
+      return "function(a, b) { return (a % b + +b) % b; }";
     },
     hasProp: function() {
       return '{}.hasOwnProperty';
diff --git a/src/nodes.coffee b/src/nodes.coffee
index 5d1d31c544..be1484db21 100644
--- a/src/nodes.coffee
+++ b/src/nodes.coffee
@@ -2194,7 +2194,7 @@ UTILITIES =
   "
 
   modulo: -> """
-    function(a, b) { return (a % b + b) % b; }
+    function(a, b) { return (a % b + +b) % b; }
   """
 
   # Shortcuts to speed up the lookup time for native functions.
diff --git a/test/operators.coffee b/test/operators.coffee
index a16bd9f78c..6821b0df02 100644
--- a/test/operators.coffee
+++ b/test/operators.coffee
@@ -355,3 +355,8 @@ test "modulo operator compound assignment", ->
   a = -2
   a %%= 5
   eq 3, a
+
+test "modulo operator converts arguments to numbers", ->
+  eq 1, 1 %% '42'
+  eq 1, '1' %% 42
+  eq 1, '1' %% '42'