diff --git a/HISTORY.md b/HISTORY.md
index 27a60d1c4..2d417b4e0 100644
--- a/HISTORY.md
+++ b/HISTORY.md
@@ -2,6 +2,12 @@
 https://github.com/josdejong/mathjs
 
 
+## not yet released, version 0.23.1
+
+- Fixed imported, wrapped functions not accepting `null` and `undefined` as
+  function arguments.
+
+
 ## 2014-06-10, version 0.23.0
 
 - Renamed some functions (everything now has a logical, camel case name):
diff --git a/lib/function/utils/import.js b/lib/function/utils/import.js
index aebac0951..2e6ec2114 100644
--- a/lib/function/utils/import.js
+++ b/lib/function/utils/import.js
@@ -117,7 +117,8 @@ module.exports = function (math) {
         math[name] = function () {
           var args = [];
           for (var i = 0, len = arguments.length; i < len; i++) {
-            args[i] = arguments[i].valueOf();
+            var arg = arguments[i];
+            args[i] = arg && arg.valueOf();
           }
           return value.apply(math, args);
         };
diff --git a/test/function/utils/import.test.js b/test/function/utils/import.test.js
index caf934c2e..28e605982 100644
--- a/test/function/utils/import.test.js
+++ b/test/function/utils/import.test.js
@@ -59,6 +59,26 @@ describe('import', function() {
     assert.equal(math.getSizeNotWrapped(math.matrix([1,2,3])), undefined);
   });
 
+  it('wrapped imported functions should accept undefined and null', function () {
+    math.import({
+      isNull: function (obj) {
+        return obj === null;
+      }
+    }, { wrap: true });
+    assert.equal(math.isNull(null), true);
+    assert.equal(math.isNull(0), false);
+
+    math.import({
+      isUndefined: function (obj) {
+        return obj === undefined;
+      }
+    }, { wrap: true });
+    assert.equal(math.isUndefined(undefined), true);
+    assert.equal(math.isUndefined(0), false);
+    assert.equal(math.isUndefined(null), false);
+
+  });
+
   it('should extend math with numbers', function() {
     // extend math.js with numbers.js
     // examples copied from https://github.com/sjkaliski/numbers.js/blob/master/examples/statistic.js