diff --git a/sys/sys/exterrvar.h b/sys/sys/exterrvar.h
index 0a34280ff711..a4f6d5313efc 100644
--- a/sys/sys/exterrvar.h
+++ b/sys/sys/exterrvar.h
@@ -1,90 +1,92 @@
 /*-
  * SPDX-License-Identifier: BSD-2-Clause
  *
  * Copyright (c) 2025 The FreeBSD Foundation
  * All rights reserved.
  *
  * This software were developed by Konstantin Belousov <kib@FreeBSD.org>
  * under sponsorship from the FreeBSD Foundation.
  */
 
 #ifndef _SYS_EXTERRVAR_H_
 #define	_SYS_EXTERRVAR_H_
 
 #include <sys/_exterr.h>
 #include <sys/_uexterror.h>
 #include <sys/exterr_cat.h>
 
 #define	UEXTERROR_MAXLEN	256
 
 #define	UEXTERROR_VER		0x10010002
 
 #define	EXTERRCTL_ENABLE	1
 #define	EXTERRCTL_DISABLE	2
 #define	EXTERRCTL_UD		3
 
 #define	EXTERRCTLF_FORCE	0x00000001
 
 #ifdef _KERNEL
 
+struct thread;
+
 #ifndef EXTERR_CATEGORY
 #error "Specify error category before including sys/exterrvar.h"
 #endif
 
 #ifdef	EXTERR_STRINGS
 #define	SET_ERROR_MSG(mmsg)	(mmsg)
 #else
 #define	SET_ERROR_MSG(mmsg)	NULL
 #endif
 
 #define	_SET_ERROR2_KE(kep, eerror, mmsg, pp1, pp2)	({		\
 	(kep)->error = (eerror);					\
 	(kep)->cat = EXTERR_CATEGORY;					\
 	(kep)->msg = SET_ERROR_MSG(mmsg);				\
 	(kep)->p1 = (pp1);						\
 	(kep)->p2 = (pp2);						\
 	(kep)->src_line = __LINE__;					\
 	(kep)->error;							\
 })
 #define	_SET_ERROR0_KE(kep, eerror, mmsg)				\
 	_SET_ERROR2_KE(kep, eerror, mmsg, 0, 0)
 #define	_SET_ERROR1_KE(kep, eerror, mmsg, pp1)				\
 	_SET_ERROR2_KE(kep, eerror, mmsg, pp1, 0)
 
 #define	_EXTERROR_MACRO_KE(kep, eerror, mmsg, _1, _2, NAME, ...)	\
 	NAME
 #define	EXTERROR_KE(...)						\
 	_EXTERROR_MACRO_KE(__VA_ARGS__, _SET_ERROR2_KE, _SET_ERROR1_KE,	\
 	    _SET_ERROR0_KE)(__VA_ARGS__)
 
 #define	_SET_ERROR2(eerror, mmsg, pp1, pp2)				\
 	exterr_set(eerror, EXTERR_CATEGORY, SET_ERROR_MSG(mmsg),	\
 	    (uint64ptr_t)(pp1), (uint64ptr_t)(pp2), __LINE__)
 #define	_SET_ERROR0(eerror, mmsg)	_SET_ERROR2(eerror, mmsg, 0, 0)
 #define	_SET_ERROR1(eerror, mmsg, pp1)	_SET_ERROR2(eerror, mmsg, pp1, 0)
 
 #define	_EXTERROR_MACRO(eerror, mmsg, _1, _2, NAME, ...)		\
 	NAME
 #define	EXTERROR(...)							\
 	_EXTERROR_MACRO(__VA_ARGS__, _SET_ERROR2, _SET_ERROR1,		\
 	    _SET_ERROR0)(__VA_ARGS__)
 
 void exterr_clear(struct kexterr *ke);
 void exterr_db_print(struct kexterr *ke);
 int exterr_set_from(const struct kexterr *ke);
 int exterr_set(int eerror, int category, const char *mmsg, uint64ptr_t pp1,
     uint64ptr_t pp2, int line);
 int exterr_to_ue(struct thread *td, struct uexterror *ue);
 void ktrexterr(struct thread *td);
 
 #else	/* !_KERNEL */
 
 #include <sys/types.h>
 
 __BEGIN_DECLS
 int exterrctl(u_int op, u_int flags, void *ptr);
 __END_DECLS
 
 #endif	/* _KERNEL */
 
 #endif