diff --git a/py/obj.h b/py/obj.h
index 49167bfccb..332867a194 100644
--- a/py/obj.h
+++ b/py/obj.h
@@ -42,13 +42,17 @@ typedef struct _mp_obj_base_t mp_obj_base_t;
 
 #define MP_DECLARE_CONST_FUN_OBJ(obj_name) extern const mp_obj_fun_native_t obj_name
 
-#define MP_DEFINE_CONST_FUN_OBJ_VOID_PTR(obj_name, n_args_min, n_args_max, fun_name) const mp_obj_fun_native_t obj_name = {{&fun_native_type}, n_args_min, n_args_max, (void *)fun_name}
-#define MP_DEFINE_CONST_FUN_OBJ_0(obj_name, fun_name) MP_DEFINE_CONST_FUN_OBJ_VOID_PTR(obj_name, 0, 0, (mp_fun_0_t)fun_name)
-#define MP_DEFINE_CONST_FUN_OBJ_1(obj_name, fun_name) MP_DEFINE_CONST_FUN_OBJ_VOID_PTR(obj_name, 1, 1, (mp_fun_1_t)fun_name)
-#define MP_DEFINE_CONST_FUN_OBJ_2(obj_name, fun_name) MP_DEFINE_CONST_FUN_OBJ_VOID_PTR(obj_name, 2, 2, (mp_fun_2_t)fun_name)
-#define MP_DEFINE_CONST_FUN_OBJ_3(obj_name, fun_name) MP_DEFINE_CONST_FUN_OBJ_VOID_PTR(obj_name, 3, 3, (mp_fun_3_t)fun_name)
-#define MP_DEFINE_CONST_FUN_OBJ_VAR(obj_name, n_args_min, fun_name) MP_DEFINE_CONST_FUN_OBJ_VOID_PTR(obj_name, n_args_min, (~((machine_uint_t)0)), (mp_fun_var_t)fun_name)
-#define MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(obj_name, n_args_min, n_args_max, fun_name) MP_DEFINE_CONST_FUN_OBJ_VOID_PTR(obj_name, n_args_min, n_args_max, (mp_fun_var_t)fun_name)
+#define MP_DEFINE_CONST_FUN_OBJ_VOID_PTR(obj_name, is_kw, n_args_min, n_args_max, fun_name) const mp_obj_fun_native_t obj_name = {{&fun_native_type}, is_kw, n_args_min, n_args_max, (void *)fun_name}
+#define MP_DEFINE_CONST_FUN_OBJ_0(obj_name, fun_name) MP_DEFINE_CONST_FUN_OBJ_VOID_PTR(obj_name, false, 0, 0, (mp_fun_0_t)fun_name)
+#define MP_DEFINE_CONST_FUN_OBJ_1(obj_name, fun_name) MP_DEFINE_CONST_FUN_OBJ_VOID_PTR(obj_name, false, 1, 1, (mp_fun_1_t)fun_name)
+#define MP_DEFINE_CONST_FUN_OBJ_2(obj_name, fun_name) MP_DEFINE_CONST_FUN_OBJ_VOID_PTR(obj_name, false, 2, 2, (mp_fun_2_t)fun_name)
+#define MP_DEFINE_CONST_FUN_OBJ_3(obj_name, fun_name) MP_DEFINE_CONST_FUN_OBJ_VOID_PTR(obj_name, false, 3, 3, (mp_fun_3_t)fun_name)
+#define MP_DEFINE_CONST_FUN_OBJ_VAR(obj_name, n_args_min, fun_name) MP_DEFINE_CONST_FUN_OBJ_VOID_PTR(obj_name, false, n_args_min, (~((machine_uint_t)0)), (mp_fun_var_t)fun_name)
+#define MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(obj_name, n_args_min, n_args_max, fun_name) MP_DEFINE_CONST_FUN_OBJ_VOID_PTR(obj_name, false, n_args_min, n_args_max, (mp_fun_var_t)fun_name)
+#define MP_DEFINE_CONST_FUN_OBJ_KW(obj_name, fun_name) MP_DEFINE_CONST_FUN_OBJ_VOID_PTR(obj_name, true, 0, (~((machine_uint_t)0)), (mp_fun_var_t)fun_name)
+
+// Need to declare this here so we are not dependent on map.h
+struct _mp_map_t;
 
 // Type definitions for methods
 
@@ -58,10 +62,12 @@ typedef mp_obj_t (*mp_fun_2_t)(mp_obj_t, mp_obj_t);
 typedef mp_obj_t (*mp_fun_3_t)(mp_obj_t, mp_obj_t, mp_obj_t);
 typedef mp_obj_t (*mp_fun_t)(void);
 typedef mp_obj_t (*mp_fun_var_t)(int n, const mp_obj_t *);
+typedef mp_obj_t (*mp_fun_kw_t)(mp_obj_t*, struct _mp_map_t*);
 
 typedef void (*mp_print_fun_t)(void (*print)(void *env, const char *fmt, ...), void *env, mp_obj_t o);
 typedef mp_obj_t (*mp_make_new_fun_t)(mp_obj_t type_in, int n_args, const mp_obj_t *args); // args are in reverse order in the array
 typedef mp_obj_t (*mp_call_n_fun_t)(mp_obj_t fun, int n_args, const mp_obj_t *args); // args are in reverse order in the array
+typedef mp_obj_t (*mp_call_n_kw_fun_t)(mp_obj_t fun, int n_args, int n_kw, const mp_obj_t *args); // args are in reverse order in the array
 typedef mp_obj_t (*mp_unary_op_fun_t)(int op, mp_obj_t);
 typedef mp_obj_t (*mp_binary_op_fun_t)(int op, mp_obj_t, mp_obj_t);
 
@@ -77,6 +83,7 @@ struct _mp_obj_type_t {
     mp_make_new_fun_t make_new;     // to make an instance of the type
 
     mp_call_n_fun_t call_n;
+    mp_call_n_kw_fun_t call_n_kw;
     mp_unary_op_fun_t unary_op;     // can return NULL if op not supported
     mp_binary_op_fun_t binary_op;   // can return NULL if op not supported
 
@@ -120,10 +127,6 @@ extern const mp_obj_t mp_const_empty_tuple;
 extern const mp_obj_t mp_const_ellipsis;
 extern const mp_obj_t mp_const_stop_iteration; // special object indicating end of iteration (not StopIteration exception!)
 
-// Need to declare this here so we are not dependent on map.h
-
-struct _mp_map_t;
-
 // General API for objects
 
 mp_obj_t mp_obj_new_none(void);
@@ -146,8 +149,8 @@ mp_obj_t mp_obj_new_fun_asm(uint n_args, void *fun);
 mp_obj_t mp_obj_new_gen_wrap(uint n_locals, uint n_stack, mp_obj_t fun);
 mp_obj_t mp_obj_new_gen_instance(const byte *bytecode, uint n_state, int n_args, const mp_obj_t *args);
 mp_obj_t mp_obj_new_closure(mp_obj_t fun, mp_obj_t closure_tuple);
-mp_obj_t mp_obj_new_tuple(uint n, mp_obj_t *items);
-mp_obj_t mp_obj_new_tuple_reverse(uint n, mp_obj_t *items);
+mp_obj_t mp_obj_new_tuple(uint n, const mp_obj_t *items);
+mp_obj_t mp_obj_new_tuple_reverse(uint n, const mp_obj_t *items);
 mp_obj_t mp_obj_new_list(uint n, mp_obj_t *items);
 mp_obj_t mp_obj_new_list_reverse(uint n, mp_obj_t *items);
 mp_obj_t mp_obj_new_dict(int n_args);
@@ -236,7 +239,8 @@ void mp_obj_slice_get(mp_obj_t self_in, machine_int_t *start, machine_int_t *sto
 // functions
 typedef struct _mp_obj_fun_native_t { // need this so we can define const objects (to go in ROM)
     mp_obj_base_t base;
-    machine_uint_t n_args_min; // inclusive
+    bool is_kw : 1;
+    machine_uint_t n_args_min : (sizeof(machine_uint_t) - 1); // inclusive
     machine_uint_t n_args_max; // inclusive
     void *fun;
     // TODO add mp_map_t *globals
diff --git a/py/objfun.c b/py/objfun.c
index 51b4329c63..395824b046 100644
--- a/py/objfun.c
+++ b/py/objfun.c
@@ -17,9 +17,13 @@
 
 // mp_obj_fun_native_t defined in obj.h
 
+mp_obj_t fun_native_call_n_kw(mp_obj_t self_in, int n_args, int n_kw, const mp_obj_t *args);
 // args are in reverse order in the array
 mp_obj_t fun_native_call_n(mp_obj_t self_in, int n_args, const mp_obj_t *args) {
     mp_obj_fun_native_t *self = self_in;
+    if (self->is_kw) {
+        return fun_native_call_n_kw(self_in, n_args, 0, args);
+    }
     if (self->n_args_min == self->n_args_max) {
         // function requires a fixed number of arguments
 
@@ -69,10 +73,29 @@ mp_obj_t fun_native_call_n(mp_obj_t self_in, int n_args, const mp_obj_t *args) {
     }
 }
 
+mp_obj_t fun_native_call_n_kw(mp_obj_t self_in, int n_args, int n_kw, const mp_obj_t *args) {
+    mp_obj_fun_native_t *self = self_in;
+
+    if (!self->is_kw) {
+        nlr_jump(mp_obj_new_exception_msg(MP_QSTR_TypeError, "function does not take keyword arguments"));
+    }
+
+    mp_obj_t *vargs = mp_obj_new_tuple_reverse(n_args, args + 2*n_kw);
+    mp_map_t *kw_args = mp_map_new(MP_MAP_QSTR, n_kw);
+    for (int i = 0; i < 2*n_kw; i+=2) {
+        qstr name = mp_obj_str_get(args[i+1]);
+        mp_qstr_map_lookup(kw_args, name, true)->value = args[i];
+    }
+    mp_obj_t res = ((mp_fun_kw_t)self->fun)(vargs, kw_args);
+    /* TODO clean up vargs and kw_args */
+    return res;
+}
+
 const mp_obj_type_t fun_native_type = {
     { &mp_const_type },
     "function",
     .call_n = fun_native_call_n,
+    .call_n_kw = fun_native_call_n_kw,
 };
 
 mp_obj_t rt_make_function_0(mp_fun_0_t fun) {
diff --git a/py/objlist.c b/py/objlist.c
index df9e1974f9..5162fa09ff 100644
--- a/py/objlist.c
+++ b/py/objlist.c
@@ -8,6 +8,7 @@
 #include "mpconfig.h"
 #include "mpqstr.h"
 #include "obj.h"
+#include "map.h"
 #include "runtime0.h"
 #include "runtime.h"
 
@@ -120,14 +121,15 @@ static mp_obj_t list_pop(int n_args, const mp_obj_t *args) {
 }
 
 // TODO make this conform to CPython's definition of sort
-static void mp_quicksort(mp_obj_t *head, mp_obj_t *tail, mp_obj_t key_fn) {
+static void mp_quicksort(mp_obj_t *head, mp_obj_t *tail, mp_obj_t key_fn, bool reversed) {
+    int op = reversed ? RT_COMPARE_OP_MORE : RT_COMPARE_OP_LESS;
     while (head < tail) {
         mp_obj_t *h = head - 1;
         mp_obj_t *t = tail;
-        mp_obj_t v = rt_call_function_1(key_fn, tail[0]); // get pivot using key_fn
+        mp_obj_t v = key_fn == NULL ? tail[0] : rt_call_function_1(key_fn, tail[0]); // get pivot using key_fn
         for (;;) {
-            do ++h; while (rt_compare_op(RT_COMPARE_OP_LESS, rt_call_function_1(key_fn, h[0]), v) == mp_const_true);
-            do --t; while (h < t && rt_compare_op(RT_COMPARE_OP_LESS, v, rt_call_function_1(key_fn, t[0])) == mp_const_true);
+            do ++h; while (rt_compare_op(op, key_fn == NULL ? h[0] : rt_call_function_1(key_fn, h[0]), v) == mp_const_true);
+            do --t; while (h < t && rt_compare_op(op, v, key_fn == NULL ? t[0] : rt_call_function_1(key_fn, t[0])) == mp_const_true);
             if (h >= t) break;
             mp_obj_t x = h[0];
             h[0] = t[0];
@@ -136,16 +138,31 @@ static void mp_quicksort(mp_obj_t *head, mp_obj_t *tail, mp_obj_t key_fn) {
         mp_obj_t x = h[0];
         h[0] = tail[0];
         tail[0] = x;
-        mp_quicksort(head, t, key_fn);
+        mp_quicksort(head, t, key_fn, reversed);
         head = h + 1;
     }
 }
 
-static mp_obj_t list_sort(mp_obj_t self_in, mp_obj_t key_fn) {
-    assert(MP_OBJ_IS_TYPE(self_in, &list_type));
-    mp_obj_list_t *self = self_in;
+static mp_obj_t list_sort(mp_obj_t *args, mp_map_t *kwargs) {
+    mp_obj_t *args_items = NULL;
+    machine_uint_t args_len = 0;
+    qstr key_idx = qstr_from_str_static("key");
+    qstr reverse_idx = qstr_from_str_static("reverse");
+
+    assert(MP_OBJ_IS_TYPE(args, &tuple_type));
+    mp_obj_tuple_get(args, &args_len, &args_items);
+    assert(args_len >= 1);
+    if (args_len > 1) {
+        nlr_jump(mp_obj_new_exception_msg(MP_QSTR_TypeError,
+                                          "list.sort takes no positional arguments"));
+    }
+    mp_obj_list_t *self = args_items[0];
     if (self->len > 1) {
-        mp_quicksort(self->items, self->items + self->len - 1, key_fn);
+        mp_map_elem_t *keyfun = mp_qstr_map_lookup(kwargs, key_idx, false);
+        mp_map_elem_t *reverse = mp_qstr_map_lookup(kwargs, reverse_idx, false);
+        mp_quicksort(self->items, self->items + self->len - 1,
+                     keyfun ? keyfun->value : NULL,
+                     reverse && reverse->value ? rt_is_true(reverse->value) : false);
     }
     return mp_const_none; // return None, as per CPython
 }
@@ -259,7 +276,7 @@ static MP_DEFINE_CONST_FUN_OBJ_3(list_insert_obj, list_insert);
 static MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(list_pop_obj, 1, 2, list_pop);
 static MP_DEFINE_CONST_FUN_OBJ_2(list_remove_obj, list_remove);
 static MP_DEFINE_CONST_FUN_OBJ_1(list_reverse_obj, list_reverse);
-static MP_DEFINE_CONST_FUN_OBJ_2(list_sort_obj, list_sort);
+static MP_DEFINE_CONST_FUN_OBJ_KW(list_sort_obj, list_sort);
 
 static const mp_method_t list_type_methods[] = {
     { "append", &list_append_obj },
diff --git a/py/objtuple.c b/py/objtuple.c
index 593b14e9f5..0050fc5ea0 100644
--- a/py/objtuple.c
+++ b/py/objtuple.c
@@ -109,7 +109,7 @@ const mp_obj_type_t tuple_type = {
 static const mp_obj_tuple_t empty_tuple_obj = {{&tuple_type}, 0};
 const mp_obj_t mp_const_empty_tuple = (mp_obj_t)&empty_tuple_obj;
 
-mp_obj_t mp_obj_new_tuple(uint n, mp_obj_t *items) {
+mp_obj_t mp_obj_new_tuple(uint n, const mp_obj_t *items) {
     if (n == 0) {
         return mp_const_empty_tuple;
     }
@@ -122,7 +122,7 @@ mp_obj_t mp_obj_new_tuple(uint n, mp_obj_t *items) {
     return o;
 }
 
-mp_obj_t mp_obj_new_tuple_reverse(uint n, mp_obj_t *items) {
+mp_obj_t mp_obj_new_tuple_reverse(uint n, const mp_obj_t *items) {
     if (n == 0) {
         return mp_const_empty_tuple;
     }
diff --git a/py/runtime.c b/py/runtime.c
index dce8c7b96a..962d539c04 100644
--- a/py/runtime.c
+++ b/py/runtime.c
@@ -689,10 +689,20 @@ mp_obj_t rt_call_function_n(mp_obj_t fun_in, int n_args, const mp_obj_t *args) {
 
 // args are in reverse order in the array; keyword arguments come first, value then key
 // eg: (value1, key1, value0, key0, arg1, arg0)
-mp_obj_t rt_call_function_n_kw(mp_obj_t fun, uint n_args, uint n_kw, const mp_obj_t *args) {
-    // TODO
-    assert(0);
-    return mp_const_none;
+mp_obj_t rt_call_function_n_kw(mp_obj_t fun_in, uint n_args, uint n_kw, const mp_obj_t *args) {
+    // TODO merge this and _n into a single, smarter thing
+    DEBUG_OP_printf("calling function %p(n_args=%d, n_kw=%d, args=%p)\n", fun_in, n_args, n_kw, args);
+
+    if (MP_OBJ_IS_SMALL_INT(fun_in)) {
+        nlr_jump(mp_obj_new_exception_msg(MP_QSTR_TypeError, "'int' object is not callable"));
+    } else {
+        mp_obj_base_t *fun = fun_in;
+        if (fun->type->call_n_kw != NULL) {
+            return fun->type->call_n_kw(fun_in, n_args, n_kw, args);
+        } else {
+            nlr_jump(mp_obj_new_exception_msg_1_arg(MP_QSTR_TypeError, "'%s' object is not callable", fun->type->name));
+        }
+    }
 }
 
 // args contains: arg(n_args-1)  arg(n_args-2)  ...  arg(0)  self/NULL  fun
diff --git a/tests/basics/tests/list_sort.py b/tests/basics/tests/list_sort.py
new file mode 100644
index 0000000000..eff12b9c80
--- /dev/null
+++ b/tests/basics/tests/list_sort.py
@@ -0,0 +1,13 @@
+l = [1, 3, 2, 5]
+print(l)
+l.sort()
+print(l)
+l.sort(key=lambda x: -x)
+print(l)
+l.sort(key=lambda x: -x, reverse=True)
+print(l)
+l.sort(reverse=True)
+print(l)
+l.sort(reverse=False)
+print(l)
+