diff --git a/extra/assembly/amd/test/test_custom_kernel.py b/extra/assembly/amd/test/test_custom_kernel.py
index 199cbc5f5f..6102b217c7 100644
--- a/extra/assembly/amd/test/test_custom_kernel.py
+++ b/extra/assembly/amd/test/test_custom_kernel.py
@@ -34,6 +34,26 @@ def custom_add_one(A:UOp, arch:str) -> UOp:
   sink = UOp.sink(A.base, threads, arg=KernelInfo(name:=f"custom_add_one_{A.size}", estimates=Estimates(ops=A.size, mem=A.size*4*2)))
   return UOp(Ops.PROGRAM, src=(sink, UOp(Ops.DEVICE, arg="AMD"), UOp(Ops.LINEAR, src=(*sink.src, sink)), *assemble_insts(insts, name, arch)))
 
+def custom_add_var(A:UOp, B:UOp, arch:str) -> UOp:
+  A,B = A.flatten(), B.flatten()
+  assert A.dtype.base == dtypes.uint32, f"buffer dtype must be uint32, got {A.dtype}"
+  threads = UOp.special(A.size, "lidx0")
+  var = UOp.variable("var", 0, 10)
+  insts = [
+    s_load_b128(s[4:7], s[0:1]),
+    s_load_b32(s[8], s[0:1], offset=0x10), # all threads load the same variable
+    s_waitcnt(lgkmcnt=0),
+    v_lshlrev_b32_e32(v[0], 2, v[0]), # element offset, different per thread
+    global_load_b32(v[1], v[0], saddr=s[6:7]),
+    s_waitcnt(vmcnt=0),
+    v_add_nc_u32_e32(v[1], s[8], v[1]),
+    global_store_b32(addr=v[0], data=v[1], saddr=s[4:5]),
+    s_endpgm(),
+  ]
+  sink = UOp.sink(A.base, B.base, var, threads, arg=KernelInfo(name:=f"custom_add_one_{A.size}"))
+  return UOp(Ops.PROGRAM, src=(sink, UOp(Ops.DEVICE, arg="AMD"), UOp(Ops.LINEAR, src=(*sink.src, sink)),
+                               *assemble_insts(insts, name, arch, kernarg_size=16)))
+
 class TestCustomKernel(unittest.TestCase):
   def test_simple(self):
     a = Tensor.full((16, 16), 1.).contiguous().realize()
@@ -44,5 +64,14 @@ class TestCustomKernel(unittest.TestCase):
     ei.run()
     self.assertTrue((a.numpy() == 2.).all())
 
+  def test_variable(self):
+    b = Tensor.full((16, 16), 1, dtype=dtypes.uint32).contiguous().realize()
+    a = Tensor.zeros_like(b).contiguous().realize()
+    a = Tensor.custom_kernel(a, b, fxn=functools.partial(custom_add_var, arch=Device[Device.DEFAULT].arch))[0]
+    ei = a.schedule()[-1].lower()
+    for i in range(4):
+      ei.run({"var":i})
+      self.assertTrue((a.numpy() == 1+i).all())
+
 if __name__ == "__main__":
   unittest.main()