diff --git a/sys/kern/subr_pcu.c b/sys/kern/subr_pcu.c
index 27248e31c7d6..fa4d1a457ad4 100644
--- a/sys/kern/subr_pcu.c
+++ b/sys/kern/subr_pcu.c
@@ -1,4 +1,4 @@
-/*	$NetBSD: subr_pcu.c,v 1.23 2020/08/01 02:05:45 riastradh Exp $	*/
+/*	$NetBSD: subr_pcu.c,v 1.24 2020/08/07 18:46:00 christos Exp $	*/
 
 /*-
  * Copyright (c) 2011, 2014 The NetBSD Foundation, Inc.
@@ -52,7 +52,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: subr_pcu.c,v 1.23 2020/08/01 02:05:45 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: subr_pcu.c,v 1.24 2020/08/07 18:46:00 christos Exp $");
 
 #include <sys/param.h>
 #include <sys/cpu.h>
@@ -88,6 +88,7 @@ typedef struct {
 /* PCU operations structure provided by the MD code. */
 extern const pcu_ops_t * const pcu_ops_md_defs[];
 
+#ifdef DIAGNOSTIC
 /*
  * pcu_available_p: true if lwp is allowed to use PCU state.
  */
@@ -98,6 +99,7 @@ pcu_available_p(struct lwp *l)
 	/* XXX Not sure this is safe unless l is locked!  */
 	return (l->l_flag & (LW_SYSTEM|LW_SYSTEM_FPU)) != LW_SYSTEM;
 }
+#endif
 
 /*
  * pcu_switchpoint: release PCU state if the LWP is being run on another CPU.