diff --git a/sys/kern/subr_autoconf.c b/sys/kern/subr_autoconf.c
index 121a18242abe..e447cae0a468 100644
--- a/sys/kern/subr_autoconf.c
+++ b/sys/kern/subr_autoconf.c
@@ -1958,9 +1958,14 @@ out:	mutex_exit(&config_misc_lock);
 static void
 config_detach_exit(device_t dev)
 {
+	struct lwp *det __diagused;
 
 	mutex_enter(&config_misc_lock);
-	KASSERT(dev->dv_detaching == curlwp);
+	KASSERTMSG((det = dev->dv_detaching) == curlwp,
+	    "lwp %ld [%s] @ %p detaching",
+	    (long)det->l_lid,
+	    (det->l_name ? det->l_name : det->l_proc->p_comm),
+	    det);
 	dev->dv_detaching = NULL;
 	cv_broadcast(&config_misc_cv);
 	mutex_exit(&config_misc_lock);
@@ -2171,9 +2176,14 @@ out:
 void
 config_detach_commit(device_t dev)
 {
+	struct lwp *det __diagused;
 
 	mutex_enter(&config_misc_lock);
-	KASSERT(dev->dv_detaching == curlwp);
+	KASSERTMSG((det = dev->dv_detaching) == curlwp,
+	    "lwp %ld [%s] @ %p detaching",
+	    (long)det->l_lid,
+	    (det->l_name ? det->l_name : det->l_proc->p_comm),
+	    det);
 	dev->dv_detached = true;
 	cv_broadcast(&config_misc_cv);
 	mutex_exit(&config_misc_lock);