diff --git a/grumpy-runtime-src/runtime/builtin_types.go b/grumpy-runtime-src/runtime/builtin_types.go
index 888951e7..6fe1c107 100644
--- a/grumpy-runtime-src/runtime/builtin_types.go
+++ b/grumpy-runtime-src/runtime/builtin_types.go
@@ -669,7 +669,7 @@ func builtinSetAttr(f *Frame, args Args, _ KWArgs) (*Object, *BaseException) {
 	return None, SetAttr(f, args[0], toStrUnsafe(args[1]), args[2])
 }
 
-func builtinSorted(f *Frame, args Args, _ KWArgs) (*Object, *BaseException) {
+func builtinSorted(f *Frame, args Args, kwargs KWArgs) (*Object, *BaseException) {
 	// TODO: Support (cmp=None, key=None, reverse=False)
 	if raised := checkFunctionArgs(f, "sorted", args, ObjectType); raised != nil {
 		return nil, raised
@@ -679,6 +679,14 @@ func builtinSorted(f *Frame, args Args, _ KWArgs) (*Object, *BaseException) {
 		return nil, raised
 	}
 	toListUnsafe(result).Sort(f)
+	// Implement reverse.
+	reverse, raised := IsTrue(f, kwargs.get("reverse", None))
+	if raised != nil {
+		return nil, raised
+	}
+	if reverse {
+		toListUnsafe(result).Reverse()
+	}
 	return result, nil
 }
 
diff --git a/grumpy-runtime-src/runtime/builtin_types_test.go b/grumpy-runtime-src/runtime/builtin_types_test.go
index 732db19d..0ab97248 100644
--- a/grumpy-runtime-src/runtime/builtin_types_test.go
+++ b/grumpy-runtime-src/runtime/builtin_types_test.go
@@ -328,6 +328,11 @@ func TestBuiltinFuncs(t *testing.T) {
 		{f: "sorted", args: wrapArgs(newTestDict("foo", 1, "bar", 2)), want: newTestList("bar", "foo").ToObject()},
 		{f: "sorted", args: wrapArgs(1), wantExc: mustCreateException(TypeErrorType, "'int' object is not iterable")},
 		{f: "sorted", args: wrapArgs(newTestList("foo", "bar"), 2), wantExc: mustCreateException(TypeErrorType, "'sorted' requires 1 arguments")},
+		{f: "sorted", args: wrapArgs(newTestList(1, 2, 0, 3)), kwargs: wrapKWArgs("reverse", False), want: newTestRange(4).ToObject()},
+		{f: "sorted", args: wrapArgs(newTestList(1, 2, 0, 3)), kwargs: wrapKWArgs("reverse", 0), want: newTestRange(4).ToObject()},
+		{f: "sorted", args: wrapArgs(newTestList(1, 2, 0, 3)), kwargs: wrapKWArgs("reverse", None), want: newTestRange(4).ToObject()},
+		{f: "sorted", args: wrapArgs(newTestList(1, 2, 0, 3)), kwargs: wrapKWArgs("reverse", True), want: newTestList(3, 2, 1, 0).ToObject()},
+		{f: "sorted", args: wrapArgs(newTestList(1, 2, 0, 3)), kwargs: wrapKWArgs("reverse", 1), want: newTestList(3, 2, 1, 0).ToObject()},
 		{f: "sum", args: wrapArgs(newTestList(1, 2, 3, 4)), want: NewInt(10).ToObject()},
 		{f: "sum", args: wrapArgs(newTestList(1, 2), 3), want: NewFloat(6).ToObject()},
 		{f: "sum", args: wrapArgs(newTestList(2, 1.1)), want: NewFloat(3.1).ToObject()},
diff --git a/grumpy-runtime-src/runtime/list.go b/grumpy-runtime-src/runtime/list.go
index 41e4c442..72b26a77 100644
--- a/grumpy-runtime-src/runtime/list.go
+++ b/grumpy-runtime-src/runtime/list.go
@@ -61,6 +61,17 @@ func (l *List) Append(o *Object) {
 	l.mutex.Unlock()
 }
 
+// Reverse the list in place.
+func (l *List) Reverse() {
+	l.mutex.Lock()
+	halfLen := len(l.elems) / 2
+	for i := 0; i < halfLen; i++ {
+		j := len(l.elems) - i - 1
+		l.elems[i], l.elems[j] = l.elems[j], l.elems[i]
+	}
+	l.mutex.Unlock()
+}
+
 // DelItem removes the index'th element of l.
 func (l *List) DelItem(f *Frame, index int) *BaseException {
 	l.mutex.Lock()
@@ -485,13 +496,7 @@ func listReverse(f *Frame, args Args, _ KWArgs) (*Object, *BaseException) {
 		return nil, raised
 	}
 	l := toListUnsafe(args[0])
-	l.mutex.Lock()
-	halfLen := len(l.elems) / 2
-	for i := 0; i < halfLen; i++ {
-		j := len(l.elems) - i - 1
-		l.elems[i], l.elems[j] = l.elems[j], l.elems[i]
-	}
-	l.mutex.Unlock()
+	l.Reverse()
 	return None, nil
 }
 
diff --git a/grumpy-runtime-src/testing/builtin_test.py b/grumpy-runtime-src/testing/builtin_test.py
index c7932682..5f099111 100644
--- a/grumpy-runtime-src/testing/builtin_test.py
+++ b/grumpy-runtime-src/testing/builtin_test.py
@@ -310,6 +310,9 @@ class Foo(object):
 assert sorted(["a", "e", "c", "b"]) == ["a", "b", "c", "e"]
 assert sorted((3, 1, 5, 2, 4)) == [1, 2, 3, 4, 5]
 assert sorted({"foo": 1, "bar": 2}) == ["bar", "foo"]
+assert sorted([1, 2], reverse=True) == [2, 1]
+assert sorted([1, 2], reverse=42) == [2, 1]
+assert sorted([1, 2], reverse=0) == [1, 2]
 
 # Test zip