diff --git a/py/map.c b/py/map.c
index e44cf33d26..524b6c8a5b 100644
--- a/py/map.c
+++ b/py/map.c
@@ -132,9 +132,29 @@ void mp_set_init(mp_set_t *set, int n) {
     set->table = m_new0(mp_obj_t, set->alloc);
 }
 
+static void mp_set_rehash(mp_set_t *set) {
+    int old_alloc = set->alloc;
+    mp_obj_t *old_table = set->table;
+    set->alloc = get_doubling_prime_greater_or_equal_to(set->alloc + 1);
+    set->used = 0;
+    set->table = m_new0(mp_obj_t, set->alloc);
+    for (int i = 0; i < old_alloc; i++) {
+        if (old_table[i] != NULL) {
+            mp_set_lookup(set, old_table[i], true);
+        }
+    }
+    m_del(mp_obj_t, old_table, old_alloc);
+}
+
 mp_obj_t mp_set_lookup(mp_set_t *set, mp_obj_t index, bool add_if_not_found) {
     int hash = mp_obj_hash(index);
-    assert(set->alloc); /* FIXME: if alloc is ever 0 when doing a lookup, this'll fail: */
+    if (set->alloc == 0) {
+        if (add_if_not_found) {
+            mp_set_rehash(set);
+        } else {
+            return NULL;
+        }
+    }
     int pos = hash % set->alloc;
     for (;;) {
         mp_obj_t elem = set->table[pos];
@@ -143,17 +163,7 @@ mp_obj_t mp_set_lookup(mp_set_t *set, mp_obj_t index, bool add_if_not_found) {
             if (add_if_not_found) {
                 if (set->used + 1 >= set->alloc) {
                     // not enough room in table, rehash it
-                    int old_alloc = set->alloc;
-                    mp_obj_t *old_table = set->table;
-                    set->alloc = get_doubling_prime_greater_or_equal_to(set->alloc + 1);
-                    set->used = 0;
-                    set->table = m_new(mp_obj_t, set->alloc);
-                    for (int i = 0; i < old_alloc; i++) {
-                        if (old_table[i] != NULL) {
-                            mp_set_lookup(set, old_table[i], true);
-                        }
-                    }
-                    m_del(mp_obj_t, old_table, old_alloc);
+                    mp_set_rehash(set);
                     // restart the search for the new element
                     pos = hash % set->alloc;
                 } else {
@@ -173,3 +183,13 @@ mp_obj_t mp_set_lookup(mp_set_t *set, mp_obj_t index, bool add_if_not_found) {
         }
     }
 }
+
+void mp_set_clear(mp_set_t *set) {
+    set->used = 0;
+    machine_uint_t a = set->alloc;
+    set->alloc = 0;
+    set->table = m_renew(mp_obj_t, set->table, a, set->alloc);
+    for (uint i=0; i<set->alloc; i++) {
+        set->table[i] = NULL;
+    }
+}
diff --git a/py/map.h b/py/map.h
index 5ce4e835b6..ba6bf9e6ee 100644
--- a/py/map.h
+++ b/py/map.h
@@ -32,3 +32,4 @@ void mp_map_clear(mp_map_t *map);
 
 void mp_set_init(mp_set_t *set, int n);
 mp_obj_t mp_set_lookup(mp_set_t *set, mp_obj_t index, bool add_if_not_found);
+void mp_set_clear(mp_set_t *set);
diff --git a/py/objset.c b/py/objset.c
index a74d1eb6a3..8bd006a761 100644
--- a/py/objset.c
+++ b/py/objset.c
@@ -104,6 +104,16 @@ static mp_obj_t set_add(mp_obj_t self_in, mp_obj_t item) {
 }
 static MP_DEFINE_CONST_FUN_OBJ_2(set_add_obj, set_add);
 
+static mp_obj_t set_clear(mp_obj_t self_in) {
+    assert(MP_OBJ_IS_TYPE(self_in, &set_type));
+    mp_obj_set_t *self = self_in;
+
+    mp_set_clear(&self->set);
+
+    return mp_const_none;
+}
+static MP_DEFINE_CONST_FUN_OBJ_1(set_clear_obj, set_clear);
+
 
 /******************************************************************************/
 /* set constructors & public C API                                            */
@@ -111,6 +121,7 @@ static MP_DEFINE_CONST_FUN_OBJ_2(set_add_obj, set_add);
 
 static const mp_method_t set_type_methods[] = {
     { "add", &set_add_obj },
+    { "clear", &set_clear_obj },
     { NULL, NULL }, // end-of-list sentinel
 };
 
diff --git a/tests/basics/tests/set_clear.py b/tests/basics/tests/set_clear.py
new file mode 100644
index 0000000000..6fda93f0fb
--- /dev/null
+++ b/tests/basics/tests/set_clear.py
@@ -0,0 +1,3 @@
+s = {1, 2, 3, 4}
+print(s.clear())
+print(list(s))