diff --git a/test/test_allocators.py b/test/test_allocators.py
index 74119a90f3..849ccbb96a 100644
--- a/test/test_allocators.py
+++ b/test/test_allocators.py
@@ -174,5 +174,15 @@ class TestAllocators(unittest.TestCase):
     test()
     check_gc()
 
+  def test_lru_allocator_massive_buffer(self):
+    with self.assertRaises(AssertionError) as context: alloc(allocator := FakeAllocator(), size := 1e13, dtypes.int8)
+    self.assertEqual(str(context.exception), f"out of memory - requested: {size/1e9:5.2f} GB, available: {allocator._get_cur_free_space('0')/1e9:5.2f} GB")
+
+  @unittest.skipIf(Device.DEFAULT != "METAL", "only applies to Metal")
+  def test_lru_allocator_metal_max_buffer_length(self):
+    from tinygrad.runtime.ops_metal import METAL
+    with self.assertRaises(AssertionError) as context: METAL.allocator._do_alloc(buf_len := (max_buf_len := METAL.device.maxBufferLength()+1), dtypes.int8, '0')
+    self.assertEqual(str(context.exception), f"Buffer length of {buf_len/1e9:5.2f} GB exceeds Metal's max buffer length of {max_buf_len/1e9:5.2f} GB.")
+
 if __name__ == "__main__":
   unittest.main()
diff --git a/tinygrad/runtime/lib.py b/tinygrad/runtime/lib.py
index 4fe63486c4..e4d236a916 100644
--- a/tinygrad/runtime/lib.py
+++ b/tinygrad/runtime/lib.py
@@ -80,6 +80,7 @@ class LRUAllocator:
     while len(self.aging_order[device]) and self._get_cur_free_space(device) < space_to_free: # When OOM removing lru buffers.
       bucket, epoch = self.aging_order[device].popleft()
       if self.cached_buffers[bucket] and self.cached_buffers[bucket][-1][1] == epoch: self._free_buffer(self.cached_buffers[bucket].pop()[0]) # Free cached buffer if it is still in cache.
+    assert (curr_free := self._get_cur_free_space(device)) > space_to_free, f"out of memory - requested: {space_to_free/1e9:5.2f} GB, available: {curr_free/1e9:5.2f} GB"
 
   def _alloc_buffer(self, size, dtype, device, **kwargs):
     self.ensure_has_free_space(size*dtype.itemsize, device)
diff --git a/tinygrad/runtime/ops_metal.py b/tinygrad/runtime/ops_metal.py
index 4e07079c54..c3771c86b1 100644
--- a/tinygrad/runtime/ops_metal.py
+++ b/tinygrad/runtime/ops_metal.py
@@ -10,7 +10,12 @@ from tinygrad.runtime.lib import RawBufferMapped, RawBuffer, LRUAllocator
 from tinygrad.shape.symbolic import Variable, Node
 
 class MetalAllocator(LRUAllocator):
-  def _do_alloc(self, size, dtype, device, **kwargs): return METAL.device.newBufferWithLength_options_(size*dtype.itemsize, Metal.MTLResourceStorageModeShared)
+  def _do_alloc(self, size, dtype, device, **kwargs):
+    buf_len, max_buf_len = size*dtype.itemsize, METAL.device.maxBufferLength()
+    assert buf_len < max_buf_len, f"Buffer length of {buf_len/1e9:5.2f} GB exceeds Metal's max buffer length of {max_buf_len/1e9:5.2f} GB."
+    buf = METAL.device.newBufferWithLength_options_(buf_len, Metal.MTLResourceStorageModeShared)
+    assert buf, f"Metal buffer allocation failed with {buf}."
+    return buf
   def _do_free(self, buf): buf.release()
   def _cached_bufkey(self, size, dtype, device): return (device, size*dtype.itemsize) # Buffers of the same length could be reused, no matter what dtype.