diff --git a/src/fs/ntapi_tt_mount.c b/src/fs/ntapi_tt_mount.c
index f5ae113..448841e 100644
--- a/src/fs/ntapi_tt_mount.c
+++ b/src/fs/ntapi_tt_mount.c
@@ -105,7 +105,7 @@ static int32_t __stdcall __tt_get_dos_drive_device_or_root_handle(
 	else
 		return NT_STATUS_INVALID_PARAMETER_2;
 
-	dos_name.strlen = ((size_t)(&((_dos_name_buffer *)0)->root));
+	dos_name.strlen = __offsetof(_dos_name_buffer,root);
 	dos_name.maxlen = 0;
 	dos_name.buffer = &(dos_name_buffer.global_prefix[0]);
 
@@ -232,7 +232,7 @@ int32_t __stdcall	__ntapi_tt_get_dos_drive_mount_points(
 	dev_mount_point->symlink_name_length = 0;
 	dev_mount_point->unique_id_offset    = 0;
 	dev_mount_point->unique_id_length    = 0;
-	dev_mount_point->device_name_offset  = ((size_t)(&((nt_mount_point_param *)0)->device_name));
+	dev_mount_point->device_name_offset  = __offsetof(nt_mount_point_param,device_name);
 	dev_mount_point->device_name_length  = dev_name->name_length;
 	dev_mount_point->mount_points_offset = 0;
 
diff --git a/src/fs/ntapi_tt_stat.c b/src/fs/ntapi_tt_stat.c
index cab84c3..088adf6 100644
--- a/src/fs/ntapi_tt_stat.c
+++ b/src/fs/ntapi_tt_stat.c
@@ -56,7 +56,7 @@ int32_t __stdcall __ntapi_tt_stat(
 	__ntapi->tt_aligned_block_memcpy(
 		(uintptr_t *)stat,
 		(uintptr_t *)buffer,
-		((size_t)(&((nt_fai *)0)->name_info)));
+		__offsetof(nt_fai,name_info));
 
 	/* record volume-relative file name length */
 	fai = (nt_fai *)buffer;
diff --git a/src/internal/ntapi_impl.h b/src/internal/ntapi_impl.h
index 4c26f55..791dbc1 100644
--- a/src/internal/ntapi_impl.h
+++ b/src/internal/ntapi_impl.h
@@ -145,7 +145,7 @@ int32_t __ntapi_tt_open_dir_utf8(void ** hfile, void * hat, const char * arg, in
 int __ntapi_ipc_page_alloc(struct dalist_ex * dlist, void ** addr, size_t * alloc_size);
 
 /* debug */
-#define __ntidx(x) (&(((ntapi_vtbl *)0)->x)) / sizeof(size_t)
+#define __ntidx(x) __offsetof(ntapi_vtbl,x) / sizeof(size_t)
 
 
 #endif
diff --git a/src/msq/ntapi_msq_connect.c b/src/msq/ntapi_msq_connect.c
index c4a0f98..301adfa 100644
--- a/src/msq/ntapi_msq_connect.c
+++ b/src/msq/ntapi_msq_connect.c
@@ -114,7 +114,7 @@ static int32_t __msqpid_symlink_set(
 	__ntapi->tt_port_name_from_attr(
 		&svcname,&msqctl->attr);
 
-	str.strlen = (uint16_t)(size_t)(&(((nt_port_name *)0)->null_termination));
+	str.strlen = (uint16_t)(__offsetof(nt_port_name,null_termination));
 	str.maxlen = sizeof(nt_port_name);
 	str.buffer = svcname.base_named_objects;
 
diff --git a/src/sem/ntapi_sem_connect.c b/src/sem/ntapi_sem_connect.c
index 2dc9a94..33a4541 100644
--- a/src/sem/ntapi_sem_connect.c
+++ b/src/sem/ntapi_sem_connect.c
@@ -114,7 +114,7 @@ static int32_t __sempid_symlink_set(
 	__ntapi->tt_port_name_from_attr(
 		&svcname,&semctl->attr);
 
-	str.strlen = (uint16_t)(size_t)(&(((nt_port_name *)0)->null_termination));
+	str.strlen = (uint16_t)(__offsetof(nt_port_name,null_termination));
 	str.maxlen = sizeof(nt_port_name);
 	str.buffer = svcname.base_named_objects;