diff --git a/sys/dev/iscsi/icl.c b/sys/dev/iscsi/icl.c
index 839fac5ba18d..44a049f7fbd3 100644
--- a/sys/dev/iscsi/icl.c
+++ b/sys/dev/iscsi/icl.c
@@ -138,11 +138,15 @@ icl_pdu_new(struct icl_conn *ic, int flags)
 {
 	struct icl_pdu *ip;
 
+#ifdef DIAGNOSTIC
 	refcount_acquire(&ic->ic_outstanding_pdus);
+#endif
 	ip = uma_zalloc(icl_pdu_zone, flags | M_ZERO);
 	if (ip == NULL) {
 		ICL_WARN("failed to allocate %zd bytes", sizeof(*ip));
+#ifdef DIAGNOSTIC
 		refcount_release(&ic->ic_outstanding_pdus);
+#endif
 		return (NULL);
 	}
 
@@ -162,7 +166,9 @@ icl_pdu_free(struct icl_pdu *ip)
 	m_freem(ip->ip_ahs_mbuf);
 	m_freem(ip->ip_data_mbuf);
 	uma_zfree(icl_pdu_zone, ip);
+#ifdef DIAGNOSTIC
 	refcount_release(&ic->ic_outstanding_pdus);
+#endif
 }
 
 /*
@@ -980,7 +986,9 @@ icl_conn_new(void)
 	mtx_init(&ic->ic_lock, "icl_lock", NULL, MTX_DEF);
 	cv_init(&ic->ic_send_cv, "icl_tx");
 	cv_init(&ic->ic_receive_cv, "icl_rx");
+#ifdef DIAGNOSTIC
 	refcount_init(&ic->ic_outstanding_pdus, 0);
+#endif
 	ic->ic_max_data_segment_length = ICL_MAX_DATA_SEGMENT_LENGTH;
 
 	return (ic);
diff --git a/sys/dev/iscsi/icl.h b/sys/dev/iscsi/icl.h
index 87a565269562..ab61cd8faa63 100644
--- a/sys/dev/iscsi/icl.h
+++ b/sys/dev/iscsi/icl.h
@@ -76,7 +76,9 @@ void			icl_pdu_free(struct icl_pdu *ip);
 struct icl_conn {
 	struct mtx		ic_lock;
 	struct socket		*ic_socket;
+#ifdef DIAGNOSTIC
 	volatile u_int		ic_outstanding_pdus;
+#endif
 	TAILQ_HEAD(, icl_pdu)	ic_to_send;
 	size_t			ic_receive_len;
 	int			ic_receive_state;