diff --git a/tools/libxl/libxl_arch.h b/tools/libxl/libxl_arch.h
index ee6641b3e6..6a91775b9e 100644
--- a/tools/libxl/libxl_arch.h
+++ b/tools/libxl/libxl_arch.h
@@ -74,7 +74,7 @@ void libxl__arch_domain_build_info_setdefault(libxl__gc *gc,
 
 _hidden
 int libxl__arch_passthrough_mode_setdefault(libxl__gc *gc,
-                                            uint32_t domid,
+                                     uint32_t domid /* for logging, only */,
                                             libxl_domain_config *d_config,
                                             const libxl_physinfo *physinfo);
 
diff --git a/tools/libxl/libxl_create.c b/tools/libxl/libxl_create.c
index d59ac2ab05..32d45dcef0 100644
--- a/tools/libxl/libxl_create.c
+++ b/tools/libxl/libxl_create.c
@@ -891,7 +891,7 @@ static unsigned long libxl__get_required_iommu_memory(unsigned long maxmem_kb)
 
 int libxl__domain_config_setdefault(libxl__gc *gc,
                                     libxl_domain_config *d_config,
-                                    uint32_t domid)
+                                    uint32_t domid /* for logging, only */)
 {
     libxl_ctx *ctx = libxl__gc_owner(gc);
     int ret;