diff --git a/hashmap.c b/hashmap.c
index 17b5dfd..635d4ca 100644
--- a/hashmap.c
+++ b/hashmap.c
@@ -129,6 +129,29 @@ struct hashmap *hashmap_new(size_t elsize, size_t cap,
     return map;    
 }
 
+// hashmap_clear quickly clears the map. 
+// When the update_cap is provided, the map's capacity will be updated to match
+// the currently number of allocated buckets. This is an optimization to ensure
+// that this operation does not perform any allocations.
+void hashmap_clear(struct hashmap *map, bool update_cap) {
+    map->count = 0;
+    if (update_cap) {
+        map->cap = map->nbuckets;
+    } else if (map->nbuckets != map->cap) {
+        void *new_buckets = hmmalloc(map->bucketsz*map->cap);
+        if (new_buckets) {
+            hmfree(map->buckets);
+            map->buckets = new_buckets;
+        }
+        map->nbuckets = map->cap;
+    }
+    memset(map->buckets, 0, map->bucketsz*map->nbuckets);
+    map->mask = map->nbuckets-1;
+    map->growat = map->nbuckets*0.75;
+    map->shrinkat = map->nbuckets*0.10;
+}
+
+
 static bool resize(struct hashmap *map, size_t new_cap) {
     struct hashmap *map2 = hashmap_new(map->elsize, new_cap, map->seed1, 
                                        map->seed1, map->hash, map->compare,
@@ -666,6 +689,36 @@ static void all() {
             assert(v && *v == vals[j]);
         }
     }
+
+    for (int i = 0; i < N; i++) {
+        while (true) {
+            assert(!hashmap_set(map, &vals[i]));
+            if (!hashmap_oom(map)) {
+                break;
+            }
+        }
+    }
+
+    assert(map->count != 0);
+    size_t prev_cap = map->cap;
+    hashmap_clear(map, true);
+    assert(prev_cap < map->cap);
+    assert(map->count == 0);
+
+
+    for (int i = 0; i < N; i++) {
+        while (true) {
+            assert(!hashmap_set(map, &vals[i]));
+            if (!hashmap_oom(map)) {
+                break;
+            }
+        }
+    }
+
+    prev_cap = map->cap;
+    hashmap_clear(map, false);
+    assert(prev_cap == map->cap);
+
     hashmap_free(map);
 
     xfree(vals);
diff --git a/hashmap.h b/hashmap.h
index 5be32d2..6fb083d 100644
--- a/hashmap.h
+++ b/hashmap.h
@@ -19,6 +19,7 @@ struct hashmap *hashmap_new(size_t elsize, size_t cap,
                                            void *udata),
                             void *udata);
 void hashmap_free(struct hashmap *map);
+void hashmap_clear(struct hashmap *map, bool update_cap);
 size_t hashmap_count(struct hashmap *map);
 bool hashmap_oom(struct hashmap *map);
 void *hashmap_get(struct hashmap *map, void *item);