--- a/common.c
+++ b/common.c
@@ -4155,6 +4155,11 @@ acx_l_process_data_frame_master(acx_devi
 		/* To_DS = 0, From_DS = 1 */
 		hdr->fc = WF_FC_FROMDSi + WF_FTYPE_DATAi;
 
+		/* Do we need to encrypt this? */
+		if (adev->wep_enabled) {
+			SET_BIT(hdr->fc, WF_FC_ISWEPi);
+		}
+
 		txbuf = acx_l_get_txbuf(adev, tx);
 		if (txbuf) {
 			len = RXBUF_BYTES_RCVD(adev, rxbuf);
