diff --git a/src/ant.c b/src/ant.c
index c6a6809..16d5276 100644
--- a/src/ant.c
+++ b/src/ant.c
@@ -2672,7 +2672,6 @@ static ant_offset_t dense_grow(ant_t *js, ant_value_t arr, ant_offset_t needed)
 
   obj->u.array.data = next;
   obj->u.array.cap = (uint32_t)new_cap;
-  if (obj->u.array.len > obj->u.array.cap) obj->u.array.len = obj->u.array.cap;
   obj->fast_array = 1;
   return (ant_offset_t)(uintptr_t)obj;
 }
@@ -2730,6 +2729,7 @@ shape_lookup:;
 }
 
 static inline void arr_set(ant_t *js, ant_value_t arr, ant_offset_t idx, ant_value_t val) {
+  ant_offset_t cur_len = get_array_length(js, arr);
   ant_offset_t doff = get_dense_buf(arr);
   
   if (doff) {
@@ -2756,7 +2756,7 @@ static inline void arr_set(ant_t *js, ant_value_t arr, ant_offset_t idx, ant_val
     }
     
     dense_set(js, doff, idx, val);
-    array_len_set(js, arr, idx + 1);
+    if (idx >= cur_len) array_len_set(js, arr, idx + 1);
     
     return;
   }
diff --git a/tests/test_array_sparse_descending_length.cjs b/tests/test_array_sparse_descending_length.cjs
new file mode 100644
index 0000000..1dbc448
--- /dev/null
+++ b/tests/test_array_sparse_descending_length.cjs
@@ -0,0 +1,24 @@
+const assert = require("node:assert");
+
+const arr = [];
+for (let n = 128, i = 0; i < 111; i++) {
+  arr[--n] = i;
+}
+
+assert.equal(arr.length, 128);
+assert.equal(arr[127], 0);
+assert.equal(arr[31], 96);
+assert.equal(arr[30], 97);
+assert.equal(arr[17], 110);
+assert.equal(arr[16], undefined);
+assert.equal(Object.keys(arr).length, 111);
+
+const mixed = [];
+mixed[127] = "tail";
+mixed[31] = "lower";
+
+assert.equal(mixed.length, 128);
+assert.equal(mixed[127], "tail");
+assert.equal(mixed[31], "lower");
+
+console.log("OK: sparse descending array writes preserve length");