diff --git a/src/modules/buffer.c b/src/modules/buffer.c
index fe9b4bc..3d6dc78 100644
--- a/src/modules/buffer.c
+++ b/src/modules/buffer.c
@@ -3298,7 +3298,11 @@ static ant_value_t js_buffer_writeUInt16BE(ant_t *js, ant_value_t *args, int nar
   TypedArrayData *ta = buffer_get_typedarray_data(js_getthis(js));
   if (!ta) return js_mkerr(js, "Invalid Buffer");
 
-  uint16_t value = (uint16_t)js_to_uint32(js_getnum(args[0]));
+  double number = js_to_number(js, args[0]);
+  if (!isfinite(number) || number < 0 || floor(number) != number || number > 0xffff)
+    return js_mkerr_typed(js, JS_ERR_RANGE, "value out of range");
+
+  uint16_t value = (uint16_t)number;
   size_t offset = 0;
   if (!buffer_checked_byte_offset(nargs > 1 ? args[1] : js_mkundef(), ta->byte_length, 2, &offset))
     return js_mkerr(js, "Offset out of bounds");
@@ -3317,11 +3321,15 @@ static ant_value_t js_buffer_writeUIntBE(ant_t *js, ant_value_t *args, int nargs
   if (!ta) return js_mkerr(js, "Invalid Buffer");
 
   double number = js_to_number(js, args[0]);
-  uint64_t value = (uint64_t)(isnan(number) || number < 0 ? 0 : floor(number));
   size_t byte_length = (size_t)js_getnum(args[2]);
   size_t offset = 0;
 
   if (byte_length == 0 || byte_length > 6) return js_mkerr(js, "byteLength out of range");
+  uint64_t max = (1ULL << (byte_length * 8)) - 1;
+  if (!isfinite(number) || number < 0 || floor(number) != number || number > (double)max)
+    return js_mkerr_typed(js, JS_ERR_RANGE, "value out of range");
+
+  uint64_t value = (uint64_t)number;
   if (!buffer_checked_byte_offset(args[1], ta->byte_length, byte_length, &offset))
     return js_mkerr(js, "Offset out of bounds");
 
diff --git a/tests/test_buffer_indexof.cjs b/tests/test_buffer_indexof.cjs
index b3e1a3b..55c5b08 100644
--- a/tests/test_buffer_indexof.cjs
+++ b/tests/test_buffer_indexof.cjs
@@ -41,6 +41,16 @@ function assertThrowsTypeError(fn) {
   assert.fail('expected TypeError');
 }
 
+function assertThrowsRangeError(fn) {
+  try {
+    fn();
+  } catch (error) {
+    assert.strictEqual(error instanceof RangeError, true);
+    return;
+  }
+  assert.fail('expected RangeError');
+}
+
 function assertThrows(fn) {
   try {
     fn();
@@ -61,4 +71,14 @@ assertThrowsTypeError(() => Buffer.from('abc').indexOf('a', 0, 'not-an-encoding'
   assertThrows(() => b.readUInt16BE(-1));
 }
 
+{
+  const b = Buffer.alloc(6);
+  assertThrowsRangeError(() => b.writeUInt16BE(0x10000, 0));
+  assertThrowsRangeError(() => b.writeUInt16BE(-1, 0));
+  assertThrowsRangeError(() => b.writeUIntBE(0x10000, 0, 2));
+  assertThrowsRangeError(() => b.writeUIntBE(-1, 0, 2));
+  assertThrowsRangeError(() => b.writeUIntBE(2 ** 48, 0, 6));
+  assert.deepStrictEqual([...b], [0, 0, 0, 0, 0, 0]);
+}
+
 console.log('buffer:indexof:ok');