diff --git a/httpboot.c b/httpboot.c
index ad01b8d..8b124e5 100644
--- a/httpboot.c
+++ b/httpboot.c
@@ -708,7 +708,7 @@ error:
 }
 
 EFI_STATUS
-httpboot_fetch_buffer (EFI_HANDLE image, VOID **buffer, UINTN *buf_size)
+httpboot_fetch_buffer (EFI_HANDLE image, VOID **buffer, UINT64 *buf_size)
 {
 	EFI_STATUS status;
 	EFI_HANDLE nic;
diff --git a/httpboot.h b/httpboot.h
index 79ee465..527a856 100644
--- a/httpboot.h
+++ b/httpboot.h
@@ -36,6 +36,6 @@
 
 BOOLEAN find_httpboot (EFI_DEVICE_PATH *devpath);
 
-EFI_STATUS httpboot_fetch_buffer (EFI_HANDLE image, VOID **buffer, UINTN *buf_size);
+EFI_STATUS httpboot_fetch_buffer (EFI_HANDLE image, VOID **buffer, UINT64 *buf_size);
 
 #endif