diff --git a/test/dma_buf.cpp b/test/dma_buf.cpp
index 95718a1..f8db57b 100644
--- a/test/dma_buf.cpp
+++ b/test/dma_buf.cpp
@@ -72,7 +72,7 @@ AllocateDmaBufUpTo(int dev_fd, std::uint32_t size, std::uint8_t index)
 void VerifyTooLargeIndexFails(int dev_fd)
 {
     if (TENSTORRENT_MAX_DMA_BUFS <= std::numeric_limits<decltype(tenstorrent_allocate_dma_buf_in::buf_index)>::max()) {
-        auto buf_max = AllocateDmaBuf(dev_fd, page_size(), TENSTORRENT_MAX_DMA_BUFS);
+        auto buf_max = AllocateDmaBuf(dev_fd, page_size(), (std::uint8_t)TENSTORRENT_MAX_DMA_BUFS);
         if (!std::holds_alternative<int>(buf_max))
             THROW_TEST_FAILURE("DMA buf allocation with too-large index was permitted unexpectedly.");