diff --git a/faiss/hip/utils/MergeNetworkWarp.h b/faiss/hip/utils/MergeNetworkWarp.h
index 19d94aa152..9ae5266f8c 100644
--- a/faiss/hip/utils/MergeNetworkWarp.h
+++ b/faiss/hip/utils/MergeNetworkWarp.h
@@ -164,7 +164,7 @@ template <typename K, typename V, bool Dir, typename Comp, bool Low>
 struct BitonicMergeStep<K, V, 1, Dir, Comp, Low, true> {
     static inline __device__ void merge(K k[1], V v[1]) {
         // Use warp shuffles
-        warpBitonicMergeLE16<K, V, 32, Dir, Comp, true>(k[0], v[0]);
+        warpBitonicMergeLE16<K, V, kWarpSize/2, Dir, Comp, true>(k[0], v[0]);
     }
 };