diff --git a/tests/unit/test_umma_qk_hd64.cu b/tests/unit/test_umma_qk_hd64.cu
index 8b3663e0..54fcddc2 100644
--- a/tests/unit/test_umma_qk_hd64.cu
+++ b/tests/unit/test_umma_qk_hd64.cu
@@ -107,8 +107,8 @@ test_umma_hd64(const bf16_t* __restrict__ q, const bf16_t* __restrict__ k,
         uint64_t dq = make_umma_desc_kmajor_none(q_addr, BLOCK_MN);
         uint64_t dk = make_umma_desc_kmajor_none(k_addr, BLOCK_MN);
 
-        // 4 warp leaders call MMA (same as working HD=16 test)
-        if (lane == 0) {
+        // Single thread calls MMA (gau-nernst's elect_one pattern)
+        if (tid == 0) {
             umma_ss_f16(tb, dq, dk, idesc, kt > 0);
         }
         asm volatile("tcgen05.fence::after_thread_sync;" ::: "memory");