--- a/hostapd/config_file.c
+++ b/hostapd/config_file.c
@@ -1957,6 +1957,10 @@ static int hostapd_config_fill(struct ho
 					   "ht_capab", line);
 				errors++;
 			}
+		} else if (os_strcmp(buf, "dynamic_ht40") == 0) {
+			conf->dynamic_ht40 = atoi(pos);
+			if (conf->dynamic_ht40 == 1)
+				conf->dynamic_ht40 = 1500;
 		} else if (os_strcmp(buf, "require_ht") == 0) {
 			conf->require_ht = atoi(pos);
 #endif /* CONFIG_IEEE80211N */
--- a/src/ap/ap_config.h
+++ b/src/ap/ap_config.h
@@ -434,6 +434,7 @@ struct hostapd_config {
 	int ieee80211n;
 	int secondary_channel;
 	int require_ht;
+	int dynamic_ht40;
 };
 
 
--- a/src/ap/hostapd.c
+++ b/src/ap/hostapd.c
@@ -21,6 +21,7 @@
 #include "beacon.h"
 #include "iapp.h"
 #include "ieee802_1x.h"
+#include "ieee802_11.h"
 #include "ieee802_11_auth.h"
 #include "vlan_init.h"
 #include "wpa_auth.h"
@@ -307,6 +308,7 @@ static void hostapd_cleanup_iface_pre(st
 
 static void hostapd_cleanup_iface_partial(struct hostapd_iface *iface)
 {
+	hostapd_deinit_ht(iface);
 	hostapd_free_hw_features(iface->hw_features, iface->num_hw_features);
 	iface->hw_features = NULL;
 	os_free(iface->current_rates);
--- a/src/ap/hostapd.h
+++ b/src/ap/hostapd.h
@@ -238,6 +238,9 @@ struct hostapd_iface {
 	/* Overlapping BSS information */
 	int olbc_ht;
 
+	int force_20mhz;
+	struct os_time last_20mhz_trigger;
+
 	u16 ht_op_mode;
 	void (*scan_cb)(struct hostapd_iface *iface);
 
--- a/src/ap/ieee802_11.c
+++ b/src/ap/ieee802_11.c
@@ -1205,6 +1205,9 @@ static void handle_beacon(struct hostapd
 					     sizeof(mgmt->u.beacon)), &elems,
 				      0);
 
+	if (!elems.ht_capabilities)
+		hostapd_trigger_20mhz(hapd->iface);
+
 	ap_list_process_beacon(hapd->iface, mgmt, &elems, fi);
 }
 
--- a/src/ap/ieee802_11.h
+++ b/src/ap/ieee802_11.h
@@ -73,4 +73,17 @@ u8 * hostapd_eid_time_zone(struct hostap
 int hostapd_update_time_adv(struct hostapd_data *hapd);
 void hostapd_client_poll_ok(struct hostapd_data *hapd, const u8 *addr);
 
+#ifdef CONFIG_IEEE80211N
+void hostapd_trigger_20mhz(struct hostapd_iface *iface);
+void hostapd_deinit_ht(struct hostapd_iface *iface);
+
+#else
+static inline void hostapd_deinit_ht(struct hostapd_iface *iface)
+{
+}
+static inline void hostapd_trigger_20mhz(struct hostapd_iface *iface)
+{
+}
+#endif /* CONFIG_IEEE80211N */
+
 #endif /* IEEE802_11_H */
--- a/src/ap/ieee802_11_ht.c
+++ b/src/ap/ieee802_11_ht.c
@@ -20,9 +20,11 @@
 #include "drivers/driver.h"
 #include "hostapd.h"
 #include "ap_config.h"
+#include "ap_drv_ops.h"
 #include "sta_info.h"
 #include "beacon.h"
 #include "ieee802_11.h"
+#include "utils/eloop.h"
 
 
 u8 * hostapd_eid_ht_capabilities(struct hostapd_data *hapd, u8 *eid)
@@ -70,12 +72,15 @@ u8 * hostapd_eid_ht_operation(struct hos
 
 	oper->control_chan = hapd->iconf->channel;
 	oper->operation_mode = host_to_le16(hapd->iface->ht_op_mode);
-	if (hapd->iconf->secondary_channel == 1)
-		oper->ht_param |= HT_INFO_HT_PARAM_SECONDARY_CHNL_ABOVE |
-			HT_INFO_HT_PARAM_REC_TRANS_CHNL_WIDTH;
-	if (hapd->iconf->secondary_channel == -1)
-		oper->ht_param |= HT_INFO_HT_PARAM_SECONDARY_CHNL_BELOW |
-			HT_INFO_HT_PARAM_REC_TRANS_CHNL_WIDTH;
+
+	if (!hapd->iface->force_20mhz) {
+		if (hapd->iconf->secondary_channel == 1)
+			oper->ht_param |= HT_INFO_HT_PARAM_SECONDARY_CHNL_ABOVE |
+				HT_INFO_HT_PARAM_REC_TRANS_CHNL_WIDTH;
+		if (hapd->iconf->secondary_channel == -1)
+			oper->ht_param |= HT_INFO_HT_PARAM_SECONDARY_CHNL_BELOW |
+				HT_INFO_HT_PARAM_REC_TRANS_CHNL_WIDTH;
+	}
 
 	pos += sizeof(*oper);
 
@@ -271,3 +276,80 @@ void hostapd_get_ht_capab(struct hostapd
 
 	neg_ht_cap->ht_capabilities_info = host_to_le16(cap);
 }
+
+static void hostapd_set_force_20mhz(struct hostapd_iface *iface);
+
+static void hostapd_restore_40mhz(void *eloop_data, void *user_ctx)
+{
+	struct hostapd_iface *iface = eloop_data;
+	struct os_time time;
+	int timeout;
+
+	if (!iface->last_20mhz_trigger.sec)
+	    return;
+
+	os_get_time(&time);
+	timeout = iface->last_20mhz_trigger.sec + iface->conf->dynamic_ht40 -
+		  time.sec;
+
+	if (timeout > 0) {
+		eloop_register_timeout(timeout, 0, hostapd_restore_40mhz,
+				       iface, NULL);
+		return;
+	}
+
+	iface->last_20mhz_trigger.sec = 0;
+	iface->last_20mhz_trigger.usec = 0;
+
+	iface->force_20mhz = 0;
+	hostapd_set_force_20mhz(iface);
+}
+
+static void hostapd_set_force_20mhz(struct hostapd_iface *iface)
+{
+	int secondary_channel;
+	int i;
+
+	ieee802_11_set_beacons(iface);
+
+	for (i = 0; i < iface->num_bss; i++) {
+		struct hostapd_data *hapd = iface->bss[i];
+
+		if (iface->force_20mhz)
+			secondary_channel = 0;
+		else
+			secondary_channel = hapd->iconf->secondary_channel;
+
+		if (hostapd_set_freq(hapd, hapd->iconf->hw_mode, iface->freq,
+					 hapd->iconf->channel,
+					 hapd->iconf->ieee80211n,
+					 secondary_channel)) {
+			wpa_printf(MSG_ERROR, "Could not set channel for "
+				   "kernel driver");
+		}
+	}
+}
+
+void hostapd_deinit_ht(struct hostapd_iface *iface)
+{
+	eloop_cancel_timeout(hostapd_restore_40mhz, iface, NULL);
+}
+
+void hostapd_trigger_20mhz(struct hostapd_iface *iface)
+{
+	if (!iface->conf->dynamic_ht40)
+		return;
+
+	if (!iface->force_20mhz) {
+		iface->force_20mhz = 1;
+		hostapd_set_force_20mhz(iface);
+	}
+
+	if (!iface->last_20mhz_trigger.sec) {
+		eloop_cancel_timeout(hostapd_restore_40mhz, iface, NULL);
+		eloop_register_timeout(iface->conf->dynamic_ht40, 0,
+				       hostapd_restore_40mhz, iface, NULL);
+	}
+
+	os_get_time(&iface->last_20mhz_trigger);
+}
