diff --git a/lib/BUILD b/lib/BUILD
index d5c8983..44acf46 100644
--- a/lib/BUILD
+++ b/lib/BUILD
@@ -31,17 +31,14 @@ bzl_library(
 
 bzl_library(
     name = "sets",
-    srcs = [
-        "old_sets.bzl",
-        "sets.bzl",
-    ],
+    srcs = ["sets.bzl"],
 )
 
 bzl_library(
     name = "new_sets",
     srcs = ["new_sets.bzl"],
     deps = [
-      ":dicts",
+        ":dicts",
     ],
 )
 
diff --git a/lib/old_sets.bzl b/lib/old_sets.bzl
index 2ac6c6b..20245b2 100644
--- a/lib/old_sets.bzl
+++ b/lib/old_sets.bzl
@@ -12,149 +12,6 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-"""Skylib module containing common set algorithms.
+"""Obsolete file, see sets.bzl instead."""
 
-CAUTION: Operating on sets, particularly sets contained in providers, may
-asymptotically slow down the analysis phase. While constructing large sets with
-addition/union is fast (there is no linear-time copy involved), the
-`difference` function and various comparison predicates involve linear-time
-traversals.
-
-For convenience, the functions in this module can take either sets or lists as
-inputs; operations that take lists treat them as if they were sets (i.e.,
-duplicate elements are ignored). Functions that return new sets always return
-them as the `set` type, regardless of the types of the inputs.
-"""
-
-_depset_type = type(depset())
-_list_type = type([])
-
-def _precondition_only_sets_or_lists(*args):
-    """Verifies that all arguments are either sets or lists.
-
-    The build will fail if any of the arguments is neither a set nor a list.
-
-    Args:
-      *args: A list of values that must be sets or lists.
-    """
-    for a in args:
-        t = type(a)
-        if t not in (_depset_type, _list_type):
-            fail("Expected arguments to be depset or list, but found type %s: %r" %
-                 (t, a))
-
-def _depset_to_list(val):
-    """Converts a depset to a list.
-
-    If the given value is a depset, will return the list representation of
-    the depset. Otherwise, will return the value itself.
-
-    Args:
-      val: The value to be optionally converted and returned.
-
-    Returns:
-      The converted value.
-    """
-    if type(val) == _depset_type:
-        return val.to_list()
-    else:
-        return val
-
-def _is_equal(a, b):
-    """Returns whether two sets are equal.
-
-    Args:
-      a: A depset or a list.
-      b: A depset or a list.
-
-    Returns:
-      True if `a` is equal to `b`, False otherwise.
-    """
-    _precondition_only_sets_or_lists(a, b)
-
-    # Convert both values to a depset then back to a list to remove duplicates.
-    a = _depset_to_list(depset(a))
-    b = _depset_to_list(depset(b))
-    return sorted(a) == sorted(b)
-
-def _is_subset(a, b):
-    """Returns whether `a` is a subset of `b`.
-
-    Args:
-      a: A depset or a list.
-      b: A depset or a list.
-
-    Returns:
-      True if `a` is a subset of `b`, False otherwise.
-    """
-    _precondition_only_sets_or_lists(a, b)
-    for e in _depset_to_list(a):
-        if e not in _depset_to_list(b):
-            return False
-    return True
-
-def _disjoint(a, b):
-    """Returns whether two sets are disjoint.
-
-    Two sets are disjoint if they have no elements in common.
-
-    Args:
-      a: A set or list.
-      b: A set or list.
-
-    Returns:
-      True if `a` and `b` are disjoint, False otherwise.
-    """
-    _precondition_only_sets_or_lists(a, b)
-    for e in _depset_to_list(a):
-        if e in _depset_to_list(b):
-            return False
-    return True
-
-def _intersection(a, b):
-    """Returns the intersection of two sets.
-
-    Args:
-      a: A set or list.
-      b: A set or list.
-
-    Returns:
-      A set containing the elements that are in both `a` and `b`.
-    """
-    _precondition_only_sets_or_lists(a, b)
-    return depset([e for e in _depset_to_list(a) if e in _depset_to_list(b)])
-
-def _union(*args):
-    """Returns the union of several sets.
-
-    Args:
-      *args: An arbitrary number of sets or lists.
-
-    Returns:
-      The set union of all sets or lists in `*args`.
-    """
-    _precondition_only_sets_or_lists(*args)
-    args_deps = [depset(x) if type(x) == _list_type else x for x in args]
-    return depset(transitive = args_deps)
-
-def _difference(a, b):
-    """Returns the elements in `a` that are not in `b`.
-
-    Args:
-      a: A set or list.
-      b: A set or list.
-
-    Returns:
-      A set containing the elements that are in `a` but not in `b`.
-    """
-    _precondition_only_sets_or_lists(a, b)
-    return depset([e for e in _depset_to_list(a) if e not in _depset_to_list(b)])
-
-sets = struct(
-    difference = _difference,
-    disjoint = _disjoint,
-    intersection = _intersection,
-    is_equal = _is_equal,
-    is_subset = _is_subset,
-    union = _union,
-)
+fail("old_sets.bzl has been removed, please use sets.bzl instead")
diff --git a/lib/unittest.bzl b/lib/unittest.bzl
index 4506c11..648b313 100644
--- a/lib/unittest.bzl
+++ b/lib/unittest.bzl
@@ -20,7 +20,6 @@ assertions used to within tests.
 """
 
 load(":new_sets.bzl", new_sets = "sets")
-load(":old_sets.bzl", "sets")
 load(":types.bzl", "types")
 
 # The following function should only be called from WORKSPACE files and workspace macros.
@@ -401,24 +400,6 @@ def _assert_equals(env, expected, actual, msg = None):
 def _assert_set_equals(env, expected, actual, msg = None):
     """Asserts that the given `expected` and `actual` sets are equal.
 
-    Args:
-      env: The test environment returned by `unittest.begin`.
-      expected: The expected set resulting from some computation.
-      actual: The actual set returned by some computation.
-      msg: An optional message that will be printed that describes the failure.
-          If omitted, a default will be used.
-    """
-    if type(actual) != type(depset()) or not sets.is_equal(expected, actual):
-        expectation_msg = "Expected %r, but got %r" % (expected, actual)
-        if msg:
-            full_msg = "%s (%s)" % (msg, expectation_msg)
-        else:
-            full_msg = expectation_msg
-        _fail(env, full_msg)
-
-def _assert_new_set_equals(env, expected, actual, msg = None):
-    """Asserts that the given `expected` and `actual` sets are equal.
-
     Args:
       env: The test environment returned by `unittest.begin`.
       expected: The expected set resulting from some computation.
@@ -434,6 +415,8 @@ def _assert_new_set_equals(env, expected, actual, msg = None):
             full_msg = expectation_msg
         _fail(env, full_msg)
 
+_assert_new_set_equals = _assert_set_equals
+
 def _expect_failure(env, expected_failure_msg = ""):
     """Asserts that the target under test has failed with a given error message.
 
diff --git a/tests/BUILD b/tests/BUILD
index fa159e9..4e69eca 100644
--- a/tests/BUILD
+++ b/tests/BUILD
@@ -2,7 +2,6 @@ load("//:bzl_library.bzl", "bzl_library")
 load(":build_test_tests.bzl", "build_test_test_suite")
 load(":collections_tests.bzl", "collections_test_suite")
 load(":dicts_tests.bzl", "dicts_test_suite")
-load(":old_sets_tests.bzl", "old_sets_test_suite")
 load(":new_sets_tests.bzl", "new_sets_test_suite")
 load(":partial_tests.bzl", "partial_test_suite")
 load(":paths_tests.bzl", "paths_test_suite")
@@ -26,8 +25,6 @@ collections_test_suite()
 
 dicts_test_suite()
 
-old_sets_test_suite()
-
 new_sets_test_suite()
 
 partial_test_suite()
@@ -61,7 +58,6 @@ sh_test(
         ":unittest_tests_bzl",
         "//lib:dicts.bzl",
         "//lib:new_sets.bzl",
-        "//lib:old_sets.bzl",
         "//lib:sets.bzl",
         "//lib:types.bzl",
         "//lib:unittest.bzl",
diff --git a/tests/old_sets_tests.bzl b/tests/old_sets_tests.bzl
deleted file mode 100644
index 638a9c3..0000000
--- a/tests/old_sets_tests.bzl
+++ /dev/null
@@ -1,153 +0,0 @@
-# Copyright 2017 The Bazel Authors. All rights reserved.
-#
-# Licensed under the Apache License, Version 2.0 (the "License");
-# you may not use this file except in compliance with the License.
-# You may obtain a copy of the License at
-#
-#    http://www.apache.org/licenses/LICENSE-2.0
-#
-# Unless required by applicable law or agreed to in writing, software
-# distributed under the License is distributed on an "AS IS" BASIS,
-# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-# See the License for the specific language governing permissions and
-# limitations under the License.
-
-"""Unit tests for old_sets.bzl."""
-
-load("//lib:old_sets.bzl", "sets")
-load("//lib:unittest.bzl", "asserts", "unittest")
-
-def _is_equal_test(ctx):
-    """Unit tests for sets.is_equal."""
-
-    # Note that if this test fails, the results for the other `sets` tests will
-    # be inconclusive because they use `asserts.set_equals`, which in turn calls
-    # `sets.is_equal`.
-    env = unittest.begin(ctx)
-
-    asserts.true(env, sets.is_equal([], []))
-    asserts.false(env, sets.is_equal([], [1]))
-    asserts.false(env, sets.is_equal([1], []))
-    asserts.true(env, sets.is_equal([1], [1]))
-    asserts.false(env, sets.is_equal([1], [1, 2]))
-    asserts.false(env, sets.is_equal([1], [2]))
-    asserts.false(env, sets.is_equal([1], depset([1, 2])))
-
-    # Verify that the implementation is not using == on the sets directly.
-    asserts.true(env, sets.is_equal(depset([1]), depset([1])))
-
-    # If passing a list, verify that duplicate elements are ignored.
-    asserts.true(env, sets.is_equal([1, 1], [1]))
-
-    return unittest.end(env)
-
-is_equal_test = unittest.make(_is_equal_test)
-
-def _is_subset_test(ctx):
-    """Unit tests for sets.is_subset."""
-    env = unittest.begin(ctx)
-
-    asserts.true(env, sets.is_subset([], []))
-    asserts.true(env, sets.is_subset([], [1]))
-    asserts.false(env, sets.is_subset([1], []))
-    asserts.true(env, sets.is_subset([1], [1]))
-    asserts.true(env, sets.is_subset([1], [1, 2]))
-    asserts.false(env, sets.is_subset([1], [2]))
-    asserts.true(env, sets.is_subset([1], depset([1, 2])))
-
-    # If passing a list, verify that duplicate elements are ignored.
-    asserts.true(env, sets.is_subset([1, 1], [1, 2]))
-
-    return unittest.end(env)
-
-is_subset_test = unittest.make(_is_subset_test)
-
-def _disjoint_test(ctx):
-    """Unit tests for sets.disjoint."""
-    env = unittest.begin(ctx)
-
-    asserts.true(env, sets.disjoint([], []))
-    asserts.true(env, sets.disjoint([], [1]))
-    asserts.true(env, sets.disjoint([1], []))
-    asserts.false(env, sets.disjoint([1], [1]))
-    asserts.false(env, sets.disjoint([1], [1, 2]))
-    asserts.true(env, sets.disjoint([1], [2]))
-    asserts.true(env, sets.disjoint([1], depset([2])))
-
-    # If passing a list, verify that duplicate elements are ignored.
-    asserts.false(env, sets.disjoint([1, 1], [1, 2]))
-
-    return unittest.end(env)
-
-disjoint_test = unittest.make(_disjoint_test)
-
-def _intersection_test(ctx):
-    """Unit tests for sets.intersection."""
-    env = unittest.begin(ctx)
-
-    asserts.set_equals(env, [], sets.intersection([], []))
-    asserts.set_equals(env, [], sets.intersection([], [1]))
-    asserts.set_equals(env, [], sets.intersection([1], []))
-    asserts.set_equals(env, [1], sets.intersection([1], [1]))
-    asserts.set_equals(env, [1], sets.intersection([1], [1, 2]))
-    asserts.set_equals(env, [], sets.intersection([1], [2]))
-    asserts.set_equals(env, [1], sets.intersection([1], depset([1])))
-
-    # If passing a list, verify that duplicate elements are ignored.
-    asserts.set_equals(env, [1], sets.intersection([1, 1], [1, 2]))
-
-    return unittest.end(env)
-
-intersection_test = unittest.make(_intersection_test)
-
-def _union_test(ctx):
-    """Unit tests for sets.union."""
-    env = unittest.begin(ctx)
-
-    asserts.set_equals(env, [], sets.union())
-    asserts.set_equals(env, [1], sets.union([1]))
-    asserts.set_equals(env, [], sets.union([], []))
-    asserts.set_equals(env, [1], sets.union([], [1]))
-    asserts.set_equals(env, [1], sets.union([1], []))
-    asserts.set_equals(env, [1], sets.union([1], [1]))
-    asserts.set_equals(env, [1, 2], sets.union([1], [1, 2]))
-    asserts.set_equals(env, [1, 2], sets.union([1], [2]))
-    asserts.set_equals(env, [1], sets.union([1], depset([1])))
-
-    # If passing a list, verify that duplicate elements are ignored.
-    asserts.set_equals(env, [1, 2], sets.union([1, 1], [1, 2]))
-
-    return unittest.end(env)
-
-union_test = unittest.make(_union_test)
-
-def _difference_test(ctx):
-    """Unit tests for sets.difference."""
-    env = unittest.begin(ctx)
-
-    asserts.set_equals(env, [], sets.difference([], []))
-    asserts.set_equals(env, [], sets.difference([], [1]))
-    asserts.set_equals(env, [1], sets.difference([1], []))
-    asserts.set_equals(env, [], sets.difference([1], [1]))
-    asserts.set_equals(env, [], sets.difference([1], [1, 2]))
-    asserts.set_equals(env, [1], sets.difference([1], [2]))
-    asserts.set_equals(env, [], sets.difference([1], depset([1])))
-
-    # If passing a list, verify that duplicate elements are ignored.
-    asserts.set_equals(env, [2], sets.difference([1, 2], [1, 1]))
-
-    return unittest.end(env)
-
-difference_test = unittest.make(_difference_test)
-
-def old_sets_test_suite():
-    """Creates the test targets and test suite for old_sets.bzl tests."""
-    unittest.suite(
-        "old_sets_tests",
-        disjoint_test,
-        intersection_test,
-        is_equal_test,
-        is_subset_test,
-        difference_test,
-        union_test,
-    )
diff --git a/tests/unittest_test.sh b/tests/unittest_test.sh
index a74c1df..baed490 100755
--- a/tests/unittest_test.sh
+++ b/tests/unittest_test.sh
@@ -73,7 +73,6 @@ exports_files(["*.bzl"])
 EOF
   ln -sf "$(rlocation bazel_skylib/lib/dicts.bzl)" lib/dicts.bzl
   ln -sf "$(rlocation bazel_skylib/lib/new_sets.bzl)" lib/new_sets.bzl
-  ln -sf "$(rlocation bazel_skylib/lib/old_sets.bzl)" lib/old_sets.bzl
   ln -sf "$(rlocation bazel_skylib/lib/sets.bzl)" lib/sets.bzl
   ln -sf "$(rlocation bazel_skylib/lib/types.bzl)" lib/types.bzl
   ln -sf "$(rlocation bazel_skylib/lib/unittest.bzl)" lib/unittest.bzl