diff --git a/README.md b/README.md
index b71d6ae6..b487cff1 100644
--- a/README.md
+++ b/README.md
@@ -116,7 +116,7 @@ convict provides serveral predefined formats for validation that you can use ([u
 * `url`
 * `email`
 * `ipaddress` - IPv4 and IPv6 addresses
-* `duration` - milliseconds or a human readable string (e.g. "3000", "5 days")
+* `duration` - milliseconds or a human readable string (e.g. 3000, "5 days")
 * `timestamp` - Unix timestamps or date strings recognized by [moment.js](http://momentjs.com/)
 * `nat` - positive integer (natural number)
 
diff --git a/lib/convict.js b/lib/convict.js
index 82dda858..0deae491 100644
--- a/lib/convict.js
+++ b/lib/convict.js
@@ -50,7 +50,7 @@ var types = {
     assert(validator.isIP(x), 'must be an IP address');
   }, "There is no IPv4 vs IPv6 addresses checking anymore, use \"ipaddress\" instead."),
   duration: function(x) {
-    var err_msg = 'must be a positive integer or human readable string (e.g. "3000", "5 days")';
+    var err_msg = 'must be a positive integer or human readable string (e.g. 3000, "5 days")';
     if (validator.isInt(x)) {
       assert(x >= 0, err_msg);
     } else {
diff --git a/test/cases/file_basic.json b/test/cases/file_basic.json
index 62c1b509..0c1ea3ef 100644
--- a/test/cases/file_basic.json
+++ b/test/cases/file_basic.json
@@ -2,5 +2,5 @@
   "ip": "10.0.1.101",
   "port": 8080,
   "session": "4 days",
-  "cache": "3000"
+  "cache": 3000
 }
diff --git a/test/cases/file_basic.out b/test/cases/file_basic.out
index 62c1b509..0c1ea3ef 100644
--- a/test/cases/file_basic.out
+++ b/test/cases/file_basic.out
@@ -2,5 +2,5 @@
   "ip": "10.0.1.101",
   "port": 8080,
   "session": "4 days",
-  "cache": "3000"
+  "cache": 3000
 }
diff --git a/test/format-tests.js b/test/format-tests.js
index 4f756604..4696aeef 100644
--- a/test/format-tests.js
+++ b/test/format-tests.js
@@ -36,6 +36,10 @@ describe('convict formats', function() {
           default: '2013-05-05'
         },
         duration: {
+          format: 'duration',
+          default: 604800000
+        },
+        duration2: {
           format: 'duration',
           default: '5 minutes'
         },
@@ -115,8 +119,12 @@ describe('convict formats', function() {
       val.must.be(moment('2013-05-05').valueOf());
     });
 
-    it('must handle duration', function() {
-      conf.get('foo.duration').must.be(60 * 5 * 1000);
+    it('must handle duration in milliseconds', function() {
+      conf.get('foo.duration').must.be(604800000);
+    });
+
+    it('must handle duration in a human readable string', function() {
+      conf.get('foo.duration2').must.be(60 * 5 * 1000);
     });
   });