diff --git a/sys/net80211/ieee80211.c b/sys/net80211/ieee80211.c
index a36abf1aa0d..391780ddab9 100644
--- a/sys/net80211/ieee80211.c
+++ b/sys/net80211/ieee80211.c
@@ -645,6 +645,7 @@ ieee80211_vap_setup(struct ieee80211com *ic, struct ieee80211vap *vap,
 	ieee80211_scan_vattach(vap);
 	ieee80211_regdomain_vattach(vap);
 	ieee80211_radiotap_vattach(vap);
+	ieee80211_vap_reset_erp(vap);
 	ieee80211_ratectl_set(vap, IEEE80211_RATECTL_NONE);
 
 	return 0;
@@ -2200,7 +2201,7 @@ ieee80211_setmode(struct ieee80211com *ic, enum ieee80211_phymode mode)
 		ieee80211_setbasicrates(&ic->ic_sup_rates[mode], mode);
 
 	ic->ic_curmode = mode;
-	ieee80211_reset_erp(ic);	/* reset ERP state */
+	ieee80211_reset_erp(ic);	/* reset global ERP state */
 
 	return 0;
 }
diff --git a/sys/net80211/ieee80211_node.c b/sys/net80211/ieee80211_node.c
index a1415d73ec6..f77be819f53 100644
--- a/sys/net80211/ieee80211_node.c
+++ b/sys/net80211/ieee80211_node.c
@@ -446,7 +446,7 @@ ieee80211_reset_bss(struct ieee80211vap *vap)
 
 	ieee80211_node_table_reset(&ic->ic_sta, vap);
 	/* XXX multi-bss: wrong */
-	ieee80211_reset_erp(ic);
+	ieee80211_vap_reset_erp(vap);
 
 	ni = ieee80211_alloc_node(&ic->ic_sta, vap, vap->iv_myaddr);
 	KASSERT(ni != NULL, ("unable to setup initial BSS node"));
@@ -682,7 +682,7 @@ ieee80211_ibss_merge(struct ieee80211_node *ni)
 		"%s: new bssid %s: %s preamble, %s slot time%s\n", __func__,
 		ether_sprintf(ni->ni_bssid),
 		ic->ic_flags&IEEE80211_F_SHPREAMBLE ? "short" : "long",
-		ic->ic_flags&IEEE80211_F_SHSLOT ? "short" : "long",
+		vap->iv_flags&IEEE80211_F_SHSLOT ? "short" : "long",
 		ic->ic_flags&IEEE80211_F_USEPROT ? ", protection" : ""
 	);
 	return ieee80211_sta_join1(ieee80211_ref_node(ni));
@@ -881,7 +881,7 @@ ieee80211_sta_join1(struct ieee80211_node *selbs)
 	 * the auto-select case; this should be redundant if the
 	 * mode is locked.
 	 */
-	ieee80211_reset_erp(ic);
+	ieee80211_vap_reset_erp(vap);
 	ieee80211_wme_initparams(vap);
 
 	if (vap->iv_opmode == IEEE80211_M_STA) {
@@ -2645,6 +2645,7 @@ static void
 ieee80211_node_join_11g(struct ieee80211_node *ni)
 {
 	struct ieee80211com *ic = ni->ni_ic;
+	struct ieee80211vap *vap = ni->ni_vap;
 
 	IEEE80211_LOCK_ASSERT(ic);
 
@@ -2660,14 +2661,13 @@ ieee80211_node_join_11g(struct ieee80211_node *ni)
 		IEEE80211_NOTE(ni->ni_vap, IEEE80211_MSG_ASSOC, ni,
 		    "station needs long slot time, count %d",
 		    ic->ic_longslotsta);
-		/* XXX vap's w/ conflicting needs won't work */
 		if (!IEEE80211_IS_CHAN_108G(ic->ic_bsschan)) {
 			/*
 			 * Don't force slot time when switched to turbo
 			 * mode as non-ERP stations won't be present; this
 			 * need only be done when on the normal G channel.
 			 */
-			ieee80211_set_shortslottime(ic, 0);
+			ieee80211_vap_set_shortslottime(vap, 0);
 		}
 	}
 	/*
@@ -2757,7 +2757,7 @@ ieee80211_node_join(struct ieee80211_node *ni, int resp)
 	    "station associated at aid %d: %s preamble, %s slot time%s%s%s%s%s%s%s%s",
 	    IEEE80211_NODE_AID(ni),
 	    ic->ic_flags & IEEE80211_F_SHPREAMBLE ? "short" : "long",
-	    ic->ic_flags & IEEE80211_F_SHSLOT ? "short" : "long",
+	    vap->iv_flags & IEEE80211_F_SHSLOT ? "short" : "long",
 	    ic->ic_flags & IEEE80211_F_USEPROT ? ", protection" : "",
 	    ni->ni_flags & IEEE80211_NODE_QOS ? ", QoS" : "",
 	    /* XXX update for VHT string */
@@ -2810,6 +2810,7 @@ static void
 ieee80211_node_leave_11g(struct ieee80211_node *ni)
 {
 	struct ieee80211com *ic = ni->ni_ic;
+	struct ieee80211vap *vap = ni->ni_vap;
 
 	IEEE80211_LOCK_ASSERT(ic);
 
@@ -2838,7 +2839,7 @@ ieee80211_node_leave_11g(struct ieee80211_node *ni)
 				    IEEE80211_MSG_ASSOC,
 				    "%s: re-enable use of short slot time\n",
 				    __func__);
-				ieee80211_set_shortslottime(ic, 1);
+				ieee80211_vap_set_shortslottime(vap, 1);
 			}
 		}
 	}
diff --git a/sys/net80211/ieee80211_output.c b/sys/net80211/ieee80211_output.c
index 4bb72c39b2a..22f0c58a944 100644
--- a/sys/net80211/ieee80211_output.c
+++ b/sys/net80211/ieee80211_output.c
@@ -2522,7 +2522,7 @@ ieee80211_getcapinfo(struct ieee80211vap *vap, struct ieee80211_channel *chan)
 	if ((ic->ic_flags & IEEE80211_F_SHPREAMBLE) &&
 	    IEEE80211_IS_CHAN_2GHZ(chan))
 		capinfo |= IEEE80211_CAPINFO_SHORT_PREAMBLE;
-	if (ic->ic_flags & IEEE80211_F_SHSLOT)
+	if (vap->iv_flags & IEEE80211_F_SHSLOT)
 		capinfo |= IEEE80211_CAPINFO_SHORT_SLOTTIME;
 	if (IEEE80211_IS_CHAN_5GHZ(chan) && (vap->iv_flags & IEEE80211_F_DOTH))
 		capinfo |= IEEE80211_CAPINFO_SPECTRUM_MGMT;
diff --git a/sys/net80211/ieee80211_phy.h b/sys/net80211/ieee80211_phy.h
index 1539e879335..45ff6c6b6b0 100644
--- a/sys/net80211/ieee80211_phy.h
+++ b/sys/net80211/ieee80211_phy.h
@@ -55,10 +55,25 @@
 #define IEEE80211_DUR_SHSLOT	9	/* ERP short slottime */
 #define IEEE80211_DUR_OFDM_SLOT	9	/* OFDM slottime */
 
+/*
+ * For drivers that don't implement per-VAP slot time
+ * (ie, they rely on net80211 figuring out the union
+ * between VAPs to program a single radio) - return
+ * the current radio configured slot time.
+ */
 #define IEEE80211_GET_SLOTTIME(ic) \
 	((ic->ic_flags & IEEE80211_F_SHSLOT) ? \
 	    IEEE80211_DUR_SHSLOT : IEEE80211_DUR_SLOT)
 
+/*
+ * For drivers that implement per-VAP slot time; look
+ * at the per-VAP flags to determine whether this VAP
+ * is in short or long slot time.
+ */
+#define IEEE80211_VAP_GET_SLOTTIME(vap) \
+	((vap->iv_flags & IEEE80211_F_SHSLOT) ? \
+	    IEEE80211_DUR_SHSLOT : IEEE80211_DUR_SLOT)
+
 /*
  * DIFS (microseconds).
  */
diff --git a/sys/net80211/ieee80211_proto.c b/sys/net80211/ieee80211_proto.c
index c70a159adad..ea189cfae70 100644
--- a/sys/net80211/ieee80211_proto.c
+++ b/sys/net80211/ieee80211_proto.c
@@ -244,6 +244,7 @@ static void update_promisc(void *, int);
 static void update_channel(void *, int);
 static void update_chw(void *, int);
 static void vap_update_wme(void *, int);
+static void vap_update_slot(void *, int);
 static void restart_vaps(void *, int);
 static void ieee80211_newstate_cb(void *, int);
 
@@ -340,6 +341,7 @@ ieee80211_proto_vattach(struct ieee80211vap *vap)
 	TASK_INIT(&vap->iv_nstate_task, 0, ieee80211_newstate_cb, vap);
 	TASK_INIT(&vap->iv_swbmiss_task, 0, beacon_swmiss, vap);
 	TASK_INIT(&vap->iv_wme_task, 0, vap_update_wme, vap);
+	TASK_INIT(&vap->iv_slot_task, 0, vap_update_slot, vap);
 	/*
 	 * Install default tx rate handling: no fixed rate, lowest
 	 * supported rate for mgmt and multicast frames.  Default
@@ -748,6 +750,32 @@ ieee80211_fix_rate(struct ieee80211_node *ni,
 		return IEEE80211_RV(okrate);
 }
 
+/*
+ * Reset 11g-related state.
+ *
+ * This is for per-VAP ERP/11g state.
+ *
+ * Eventually everything in ieee80211_reset_erp() will be
+ * per-VAP and in here.
+ */
+void
+ieee80211_vap_reset_erp(struct ieee80211vap *vap)
+{
+	struct ieee80211com *ic = vap->iv_ic;
+
+	/*
+	 * Short slot time is enabled only when operating in 11g
+	 * and not in an IBSS.  We must also honor whether or not
+	 * the driver is capable of doing it.
+	 */
+	ieee80211_vap_set_shortslottime(vap,
+		IEEE80211_IS_CHAN_A(ic->ic_curchan) ||
+		IEEE80211_IS_CHAN_HT(ic->ic_curchan) ||
+		(IEEE80211_IS_CHAN_ANYG(ic->ic_curchan) &&
+		vap->iv_opmode == IEEE80211_M_HOSTAP &&
+		(ic->ic_caps & IEEE80211_C_SHSLOT)));
+}
+
 /*
  * Reset 11g-related state.
  */
@@ -757,17 +785,6 @@ ieee80211_reset_erp(struct ieee80211com *ic)
 	ic->ic_flags &= ~IEEE80211_F_USEPROT;
 	ic->ic_nonerpsta = 0;
 	ic->ic_longslotsta = 0;
-	/*
-	 * Short slot time is enabled only when operating in 11g
-	 * and not in an IBSS.  We must also honor whether or not
-	 * the driver is capable of doing it.
-	 */
-	ieee80211_set_shortslottime(ic,
-		IEEE80211_IS_CHAN_A(ic->ic_curchan) ||
-		IEEE80211_IS_CHAN_HT(ic->ic_curchan) ||
-		(IEEE80211_IS_CHAN_ANYG(ic->ic_curchan) &&
-		ic->ic_opmode == IEEE80211_M_HOSTAP &&
-		(ic->ic_caps & IEEE80211_C_SHSLOT)));
 	/*
 	 * Set short preamble and ERP barker-preamble flags.
 	 */
@@ -781,19 +798,95 @@ ieee80211_reset_erp(struct ieee80211com *ic)
 	}
 }
 
+/*
+ * Deferred slot time update.
+ *
+ * For per-VAP slot time configuration, call the VAP
+ * method if the VAP requires it.  Otherwise, just call the
+ * older global method.
+ *
+ * If the per-VAP method is called then it's expected that
+ * the driver/firmware will take care of turning the per-VAP
+ * flags into slot time configuration.
+ *
+ * If the per-VAP method is not called then the global flags will be
+ * flipped into sync with the VAPs; ic_flags IEEE80211_F_SHSLOT will
+ * be set only if all of the vaps will have it set.
+ */
+static void
+vap_update_slot(void *arg, int npending)
+{
+	struct ieee80211vap *vap = arg;
+	struct ieee80211com *ic = vap->iv_ic;
+	struct ieee80211vap *iv;
+	int num_shslot = 0, num_lgslot = 0;
+
+	/*
+	 * Per-VAP path - we've already had the flags updated;
+	 * so just notify the driver and move on.
+	 */
+	if (vap->iv_updateslot != NULL) {
+		vap->iv_updateslot(vap);
+		return;
+	}
+
+	/*
+	 * Iterate over all of the VAP flags to update the
+	 * global flag.
+	 *
+	 * If all vaps have short slot enabled then flip on
+	 * short slot.  If any vap has it disabled then
+	 * we leave it globally disabled.  This should provide
+	 * correct behaviour in a multi-BSS scenario where
+	 * at least one VAP has short slot disabled for some
+	 * reason.
+	 */
+	IEEE80211_LOCK(ic);
+	TAILQ_FOREACH(iv, &ic->ic_vaps, iv_next) {
+		if (iv->iv_flags & IEEE80211_F_SHSLOT)
+			num_shslot++;
+		else
+			num_lgslot++;
+	}
+	IEEE80211_UNLOCK(ic);
+
+	/*
+	 * It looks backwards but - if the number of short slot VAPs
+	 * is zero then we're not short slot.  Else, we have one
+	 * or more short slot VAPs and we're checking to see if ANY
+	 * of them have short slot disabled.
+	 */
+	if (num_shslot == 0)
+		ic->ic_flags &= ~IEEE80211_F_SHSLOT;
+	else if (num_lgslot == 0)
+		ic->ic_flags |= IEEE80211_F_SHSLOT;
+
+	/*
+	 * Call the driver with our new global slot time flags.
+	 */
+	ic->ic_updateslot(ic);
+}
+
 /*
  * Set the short slot time state and notify the driver.
+ *
+ * This is the per-VAP slot time state.
  */
 void
-ieee80211_set_shortslottime(struct ieee80211com *ic, int onoff)
+ieee80211_vap_set_shortslottime(struct ieee80211vap *vap, int onoff)
 {
+	struct ieee80211com *ic = vap->iv_ic;
+
+	/*
+	 * Only modify the per-VAP slot time.
+	 */
 	if (onoff)
-		ic->ic_flags |= IEEE80211_F_SHSLOT;
+		vap->iv_flags |= IEEE80211_F_SHSLOT;
 	else
-		ic->ic_flags &= ~IEEE80211_F_SHSLOT;
-	/* notify driver */
-	if (ic->ic_updateslot != NULL)
-		ic->ic_updateslot(ic);
+		vap->iv_flags &= ~IEEE80211_F_SHSLOT;
+
+	/* schedule the deferred slot flag update and update */
+	ieee80211_runtask(ic, &vap->iv_slot_task);
 }
 
 /*
diff --git a/sys/net80211/ieee80211_proto.h b/sys/net80211/ieee80211_proto.h
index 9d224b1f5c1..cd927458ef4 100644
--- a/sys/net80211/ieee80211_proto.h
+++ b/sys/net80211/ieee80211_proto.h
@@ -154,8 +154,9 @@ uint16_t ieee80211_getcapinfo(struct ieee80211vap *,
 struct ieee80211_wme_state;
 uint8_t * ieee80211_add_wme_info(uint8_t *frm, struct ieee80211_wme_state *wme);
 
+void	ieee80211_vap_reset_erp(struct ieee80211vap *);
 void	ieee80211_reset_erp(struct ieee80211com *);
-void	ieee80211_set_shortslottime(struct ieee80211com *, int onoff);
+void	ieee80211_vap_set_shortslottime(struct ieee80211vap *, int onoff);
 int	ieee80211_iserp_rateset(const struct ieee80211_rateset *);
 void	ieee80211_setbasicrates(struct ieee80211_rateset *,
 		enum ieee80211_phymode);
diff --git a/sys/net80211/ieee80211_sta.c b/sys/net80211/ieee80211_sta.c
index 46ba73a9ecd..6daa4c23614 100644
--- a/sys/net80211/ieee80211_sta.c
+++ b/sys/net80211/ieee80211_sta.c
@@ -1435,7 +1435,7 @@ sta_recv_mgmt(struct ieee80211_node *ni, struct mbuf *m0, int subtype,
 				 * NB: we assume short preamble doesn't
 				 *     change dynamically
 				 */
-				ieee80211_set_shortslottime(ic,
+				ieee80211_vap_set_shortslottime(vap,
 					IEEE80211_IS_CHAN_A(ic->ic_bsschan) ||
 					(scan.capinfo & IEEE80211_CAPINFO_SHORT_SLOTTIME));
 				ni->ni_capinfo = (ni->ni_capinfo &~ IEEE80211_CAPINFO_SHORT_SLOTTIME)
@@ -1847,7 +1847,7 @@ sta_recv_mgmt(struct ieee80211_node *ni, struct mbuf *m0, int subtype,
 			ic->ic_flags &= ~IEEE80211_F_SHPREAMBLE;
 			ic->ic_flags |= IEEE80211_F_USEBARKER;
 		}
-		ieee80211_set_shortslottime(ic,
+		ieee80211_vap_set_shortslottime(vap,
 			IEEE80211_IS_CHAN_A(ic->ic_curchan) ||
 			(ni->ni_capinfo & IEEE80211_CAPINFO_SHORT_SLOTTIME));
 		/*
@@ -1866,7 +1866,7 @@ sta_recv_mgmt(struct ieee80211_node *ni, struct mbuf *m0, int subtype,
 		    ISREASSOC(subtype) ? "re" : "",
 		    IEEE80211_NODE_AID(ni),
 		    ic->ic_flags&IEEE80211_F_SHPREAMBLE ? "short" : "long",
-		    ic->ic_flags&IEEE80211_F_SHSLOT ? "short" : "long",
+		    vap->iv_flags&IEEE80211_F_SHSLOT ? "short" : "long",
 		    ic->ic_flags&IEEE80211_F_USEPROT ? ", protection" : "",
 		    ni->ni_flags & IEEE80211_NODE_QOS ? ", QoS" : "",
 		    ni->ni_flags & IEEE80211_NODE_HT ?
diff --git a/sys/net80211/ieee80211_var.h b/sys/net80211/ieee80211_var.h
index 24ffbe106ba..1fa596b2391 100644
--- a/sys/net80211/ieee80211_var.h
+++ b/sys/net80211/ieee80211_var.h
@@ -563,6 +563,10 @@ struct ieee80211vap {
 				    const struct wmeParams *wme_params);
 	struct task		iv_wme_task;	/* deferred VAP WME update */
 
+	/* update device state for 802.11 slot time change */
+	void			(*iv_updateslot)(struct ieee80211vap *);
+	struct task		iv_slot_task;	/* deferred slot time update */
+
 	uint64_t		iv_spare[6];
 };
 MALLOC_DECLARE(M_80211_VAP);