diff --git a/sys/dev/sfxge/common/efx.h b/sys/dev/sfxge/common/efx.h
index 7ffb295e40f..b4ef267af87 100644
--- a/sys/dev/sfxge/common/efx.h
+++ b/sys/dev/sfxge/common/efx.h
@@ -553,7 +553,7 @@ efx_mac_stats_update(
 	__in				efx_nic_t *enp,
 	__in				efsys_mem_t *esmp,
 	__inout_ecount(EFX_MAC_NSTATS)	efsys_stat_t *stat,
-	__out_opt			uint32_t *generationp);
+	__inout_opt			uint32_t *generationp);
 
 #endif	/* EFSYS_OPT_MAC_STATS */
 
diff --git a/sys/dev/sfxge/common/efx_mac.c b/sys/dev/sfxge/common/efx_mac.c
index a701797c80b..71c5da5ca40 100644
--- a/sys/dev/sfxge/common/efx_mac.c
+++ b/sys/dev/sfxge/common/efx_mac.c
@@ -804,7 +804,7 @@ efx_mac_stats_update(
 	__in				efx_nic_t *enp,
 	__in				efsys_mem_t *esmp,
 	__inout_ecount(EFX_MAC_NSTATS)	efsys_stat_t *essp,
-	__out_opt			uint32_t *generationp)
+	__inout_opt			uint32_t *generationp)
 {
 	efx_port_t *epp = &(enp->en_port);
 	efx_mac_ops_t *emop = epp->ep_emop;
diff --git a/sys/dev/sfxge/common/hunt_impl.h b/sys/dev/sfxge/common/hunt_impl.h
index a682e215b5f..6d0435f8366 100644
--- a/sys/dev/sfxge/common/hunt_impl.h
+++ b/sys/dev/sfxge/common/hunt_impl.h
@@ -237,7 +237,7 @@ hunt_mac_stats_update(
 	__in				efx_nic_t *enp,
 	__in				efsys_mem_t *esmp,
 	__inout_ecount(EFX_MAC_NSTATS)	efsys_stat_t *stat,
-	__out_opt			uint32_t *generationp);
+	__inout_opt			uint32_t *generationp);
 
 #endif	/* EFSYS_OPT_MAC_STATS */
 
diff --git a/sys/dev/sfxge/common/hunt_mac.c b/sys/dev/sfxge/common/hunt_mac.c
index 813729a7fb3..36baacaa9f0 100644
--- a/sys/dev/sfxge/common/hunt_mac.c
+++ b/sys/dev/sfxge/common/hunt_mac.c
@@ -372,7 +372,7 @@ hunt_mac_stats_update(
 	__in				efx_nic_t *enp,
 	__in				efsys_mem_t *esmp,
 	__inout_ecount(EFX_MAC_NSTATS)	efsys_stat_t *stat,
-	__out_opt			uint32_t *generationp)
+	__inout_opt			uint32_t *generationp)
 {
 	efx_qword_t value;
 	efx_qword_t generation_start;
diff --git a/sys/dev/sfxge/common/siena_impl.h b/sys/dev/sfxge/common/siena_impl.h
index d7cc52c0d72..85abdb8ce79 100644
--- a/sys/dev/sfxge/common/siena_impl.h
+++ b/sys/dev/sfxge/common/siena_impl.h
@@ -473,7 +473,7 @@ siena_mac_stats_update(
 	__in				efx_nic_t *enp,
 	__in				efsys_mem_t *esmp,
 	__inout_ecount(EFX_MAC_NSTATS)	efsys_stat_t *stat,
-	__out_opt			uint32_t *generationp);
+	__inout_opt			uint32_t *generationp);
 
 #endif	/* EFSYS_OPT_MAC_STATS */
 
diff --git a/sys/dev/sfxge/common/siena_mac.c b/sys/dev/sfxge/common/siena_mac.c
index f29e68c730c..5fd561004b0 100644
--- a/sys/dev/sfxge/common/siena_mac.c
+++ b/sys/dev/sfxge/common/siena_mac.c
@@ -235,7 +235,7 @@ siena_mac_stats_update(
 	__in				efx_nic_t *enp,
 	__in				efsys_mem_t *esmp,
 	__inout_ecount(EFX_MAC_NSTATS)	efsys_stat_t *stat,
-	__out_opt			uint32_t *generationp)
+	__inout_opt			uint32_t *generationp)
 {
 	efx_qword_t value;
 	efx_qword_t generation_start;