diff --git a/changelog.d/627.change.rst b/changelog.d/627.change.rst
new file mode 100644
index 000000000..9286afddc
--- /dev/null
+++ b/changelog.d/627.change.rst
@@ -0,0 +1 @@
+It's now possible to customize the behavior of ``eq`` and ``order`` by passing in a callable.
diff --git a/src/attr/_make.py b/src/attr/_make.py
index 44362c85d..ebbc061c3 100644
--- a/src/attr/_make.py
+++ b/src/attr/_make.py
@@ -1061,7 +1061,7 @@ def _add_method_dunders(self, method):
 )
 
 _EQ_ORDER_CUSTOMIZATION = (
-    "You have customized the behaviour of `eq` but not of `order`.  "
+    "You have customized the behavior of `eq` but not of `order`.  "
     "This is probably a bug."
 )
 
@@ -2484,7 +2484,7 @@ class Attribute(object):
     .. versionadded:: 20.1.0 *on_setattr*
     .. versionchanged:: 20.2.0 *inherited* is not taken into account for
         equality checks and hashing anymore.
-    .. versionadded:: 20.X.Y *eq_key* and *order_key*
+    .. versionadded:: 21.1.0 *eq_key* and *order_key*
 
     For the full version history of the fields, see `attr.ib`.
     """
@@ -2660,9 +2660,7 @@ def _setattrs(self, name_values_pairs):
         repr=True,
         cmp=None,
         eq=True,
-        # eq_key=None,
         order=False,
-        # order_key=None,
         hash=(name != "metadata"),
         init=True,
         inherited=False,
diff --git a/tests/test_make.py b/tests/test_make.py
index c9085c77b..05d0530ab 100644
--- a/tests/test_make.py
+++ b/tests/test_make.py
@@ -1927,7 +1927,7 @@ def test_order_missing_and_custom_eq(self):
         (w,) = wr.list
 
         assert (
-            "You have customized the behaviour of `eq` but not of `order`.  "
+            "You have customized the behavior of `eq` but not of `order`.  "
             "This is probably a bug." == w.message.args[0]
         )