diff --git a/headers.js b/headers.js
index 8c75edc..d786148 100644
--- a/headers.js
+++ b/headers.js
@@ -1,4 +1,5 @@
 var ZEROS = '0000000000000000000'
+var SEVENS = '7777777777777777777'
 var ZERO_OFFSET = '0'.charCodeAt(0)
 var USTAR = 'ustar\x0000'
 var MASK = parseInt('7777', 8)
@@ -92,7 +93,8 @@ var cksum = function (block) {
 
 var encodeOct = function (val, n) {
   val = val.toString(8)
-  return ZEROS.slice(0, n - val.length) + val + ' '
+  if (val.length > n) return SEVENS.slice(0, n) + ' '
+  else return ZEROS.slice(0, n - val.length) + val + ' '
 }
 
 /* Copied from the node-tar repo and modified to meet
diff --git a/test/fixtures/index.js b/test/fixtures/index.js
index eb18dbd..4e686bd 100644
--- a/test/fixtures/index.js
+++ b/test/fixtures/index.js
@@ -12,3 +12,4 @@ exports.INVALID_TGZ = path.join(__dirname, 'invalid.tgz')
 exports.SPACE_TAR_GZ = path.join(__dirname, 'space.tar')
 exports.GNU_LONG_PATH = path.join(__dirname, 'gnu-long-path.tar')
 exports.BASE_256_UID_GID = path.join(__dirname, 'base-256-uid-gid.tar')
+exports.LARGE_UID_GID = path.join(__dirname, 'large-uid-gid.tar')
diff --git a/test/fixtures/large-uid-gid.tar b/test/fixtures/large-uid-gid.tar
new file mode 100644
index 0000000..ae85a06
Binary files /dev/null and b/test/fixtures/large-uid-gid.tar differ
diff --git a/test/pack.js b/test/pack.js
index 49f7a90..946879e 100644
--- a/test/pack.js
+++ b/test/pack.js
@@ -145,6 +145,29 @@ test('long-name', function (t) {
   }))
 })
 
+test('large-uid-gid', function (t) {
+  t.plan(2)
+  var pack = tar.pack()
+
+  pack.entry({
+    name: 'test.txt',
+    mtime: new Date(1387580181000),
+    mode: parseInt('644', 8),
+    uname: 'maf',
+    gname: 'staff',
+    uid: 1000000001,
+    gid: 1000000002
+  }, 'hello world\n')
+
+  pack.finalize()
+
+  pack.pipe(concat(function (data) {
+    t.same(data.length & 511, 0)
+    t.deepEqual(data, fs.readFileSync(fixtures.LARGE_UID_GID))
+    fs.writeFileSync('/tmp/foo', data)
+  }))
+})
+
 test('unicode', function (t) {
   t.plan(2)
   var pack = tar.pack()