diff --git a/pre_commit/xargs.py b/pre_commit/xargs.py
index 89a134d2..8a632008 100644
--- a/pre_commit/xargs.py
+++ b/pre_commit/xargs.py
@@ -17,9 +17,9 @@ def _command_length(*cmd):
     full_cmd = ' '.join(cmd)
 
     # win32 uses the amount of characters, more details at:
-    # https://blogs.msdn.microsoft.com/oldnewthing/20031210-00/?p=41553/
+    # https://github.com/pre-commit/pre-commit/pull/839
     if sys.platform == 'win32':
-        return len(full_cmd)
+        return len(full_cmd.encode('utf-16le')) // 2
 
     return len(full_cmd.encode(sys.getfilesystemencoding()))
 
diff --git a/tests/xargs_test.py b/tests/xargs_test.py
index 2d2a4ba2..de16a012 100644
--- a/tests/xargs_test.py
+++ b/tests/xargs_test.py
@@ -55,7 +55,7 @@ def test_partition_limits():
 
 def test_partition_limit_win32(sys_win32_mock):
     cmd = ('ninechars',)
-    varargs = (u'😑' * 10,)
+    varargs = ('😑' * 10,)
     with mock.patch('pre_commit.xargs.sys', sys_win32_mock):
         ret = xargs.partition(cmd, varargs, _max_length=20)
 
@@ -64,7 +64,7 @@ def test_partition_limit_win32(sys_win32_mock):
 
 def test_partition_limit_linux(sys_linux_mock):
     cmd = ('ninechars',)
-    varargs = (u'😑' * 5,)
+    varargs = ('😑' * 5,)
     with mock.patch('pre_commit.xargs.sys', sys_linux_mock):
         ret = xargs.partition(cmd, varargs, _max_length=30)
 
@@ -73,7 +73,7 @@ def test_partition_limit_linux(sys_linux_mock):
 
 def test_argument_too_long_with_large_unicode(sys_linux_mock):
     cmd = ('ninechars',)
-    varargs = (u'😑' * 10,)  # 4 bytes * 10
+    varargs = ('😑' * 10,)  # 4 bytes * 10
     with mock.patch('pre_commit.xargs.sys', sys_linux_mock):
         with pytest.raises(xargs.ArgumentTooLongError):
             xargs.partition(cmd, varargs, _max_length=20)