diff --git a/sys/dev/rtwn/if_rtwnvar.h b/sys/dev/rtwn/if_rtwnvar.h
index 18ae6b4c455e..40050c3b90a5 100644
--- a/sys/dev/rtwn/if_rtwnvar.h
+++ b/sys/dev/rtwn/if_rtwnvar.h
@@ -25,8 +25,6 @@
 
 #define RTWN_TX_DESC_SIZE	64
 
-#define RTWN_TXBUFSZ		(16 * 1024)
-
 #define RTWN_BCN_MAX_SIZE	512
 #define RTWN_CAM_ENTRY_LIMIT	64
 
diff --git a/sys/dev/rtwn/usb/rtwn_usb_attach.c b/sys/dev/rtwn/usb/rtwn_usb_attach.c
index 6beed50ab357..959184e7f43a 100644
--- a/sys/dev/rtwn/usb/rtwn_usb_attach.c
+++ b/sys/dev/rtwn/usb/rtwn_usb_attach.c
@@ -155,7 +155,7 @@ rtwn_usb_alloc_tx_list(struct rtwn_softc *sc)
 	int error, i;
 
 	error = rtwn_usb_alloc_list(sc, uc->uc_tx, RTWN_USB_TX_LIST_COUNT,
-	    RTWN_TXBUFSZ);
+	    RTWN_USB_TXBUFSZ);
 	if (error != 0)
 		return (error);
 
diff --git a/sys/dev/rtwn/usb/rtwn_usb_ep.c b/sys/dev/rtwn/usb/rtwn_usb_ep.c
index 52c628d5a9a7..596265d4d4cc 100644
--- a/sys/dev/rtwn/usb/rtwn_usb_ep.c
+++ b/sys/dev/rtwn/usb/rtwn_usb_ep.c
@@ -73,7 +73,7 @@ static const struct usb_config rtwn_config_common[RTWN_N_TRANSFER] = {
 		.type = UE_BULK,
 		.endpoint = UE_ADDR_ANY,
 		.direction = UE_DIR_OUT,
-		.bufsize = RTWN_TXBUFSZ,
+		.bufsize = RTWN_USB_TXBUFSZ,
 		.flags = {
 			.ext_buffer = 1,
 			.pipe_bof = 1,
@@ -86,7 +86,7 @@ static const struct usb_config rtwn_config_common[RTWN_N_TRANSFER] = {
 		.type = UE_BULK,
 		.endpoint = UE_ADDR_ANY,
 		.direction = UE_DIR_OUT,
-		.bufsize = RTWN_TXBUFSZ,
+		.bufsize = RTWN_USB_TXBUFSZ,
 		.flags = {
 			.ext_buffer = 1,
 			.pipe_bof = 1,
@@ -99,7 +99,7 @@ static const struct usb_config rtwn_config_common[RTWN_N_TRANSFER] = {
 		.type = UE_BULK,
 		.endpoint = UE_ADDR_ANY,
 		.direction = UE_DIR_OUT,
-		.bufsize = RTWN_TXBUFSZ,
+		.bufsize = RTWN_USB_TXBUFSZ,
 		.flags = {
 			.ext_buffer = 1,
 			.pipe_bof = 1,
@@ -112,7 +112,7 @@ static const struct usb_config rtwn_config_common[RTWN_N_TRANSFER] = {
 		.type = UE_BULK,
 		.endpoint = UE_ADDR_ANY,
 		.direction = UE_DIR_OUT,
-		.bufsize = RTWN_TXBUFSZ,
+		.bufsize = RTWN_USB_TXBUFSZ,
 		.flags = {
 			.ext_buffer = 1,
 			.pipe_bof = 1,
diff --git a/sys/dev/rtwn/usb/rtwn_usb_tx.c b/sys/dev/rtwn/usb/rtwn_usb_tx.c
index c30e9e746985..2c5d55d3a56b 100644
--- a/sys/dev/rtwn/usb/rtwn_usb_tx.c
+++ b/sys/dev/rtwn/usb/rtwn_usb_tx.c
@@ -233,6 +233,9 @@ rtwn_usb_tx_start(struct rtwn_softc *sc, struct ieee80211_node *ni,
 
 	RTWN_ASSERT_LOCKED(sc);
 
+	if (m->m_pkthdr.len + sc->txdesc_len > RTWN_USB_TXBUFSZ)
+		return (EINVAL);
+
 	data = rtwn_usb_getbuf(uc);
 	if (data == NULL)
 		return (ENOBUFS);
diff --git a/sys/dev/rtwn/usb/rtwn_usb_var.h b/sys/dev/rtwn/usb/rtwn_usb_var.h
index be7f8f198834..aa0f987b7730 100644
--- a/sys/dev/rtwn/usb/rtwn_usb_var.h
+++ b/sys/dev/rtwn/usb/rtwn_usb_var.h
@@ -21,6 +21,8 @@
 #ifndef RTWN_USBVAR_H
 #define RTWN_USBVAR_H
 
+#define RTWN_USB_TXBUFSZ		(16 * 1024)
+
 #define RTWN_IFACE_INDEX		0
 
 #define RTWN_USB_RX_LIST_COUNT		1