diff --git a/subsys/bluetooth/controller/hci/hci_driver.c b/subsys/bluetooth/controller/hci/hci_driver.c
index 0a655537a4a0..1f856e56f6a8 100644
--- a/subsys/bluetooth/controller/hci/hci_driver.c
+++ b/subsys/bluetooth/controller/hci/hci_driver.c
@@ -158,8 +158,8 @@ isoal_status_t sink_sdu_alloc_hci(const struct isoal_sink    *sink_ctx,
 	struct net_buf *buf  = bt_buf_get_rx(BT_BUF_ISO_IN, K_FOREVER);
 
 	if (buf) {
-		/* Reserve space for headers */
-		net_buf_reserve(buf, SDU_HCI_HDR_SIZE);
+		/* Increase reserved space for headers */
+		net_buf_reserve(buf, SDU_HCI_HDR_SIZE + net_buf_headroom(buf));
 
 		sdu_buffer->dbuf = buf;
 		sdu_buffer->size = net_buf_tailroom(buf);
diff --git a/tests/bsim/bluetooth/audio/sysbuild.cmake b/tests/bsim/bluetooth/audio/sysbuild.cmake
index 5dfd594349c1..e5bd9d9e4255 100644
--- a/tests/bsim/bluetooth/audio/sysbuild.cmake
+++ b/tests/bsim/bluetooth/audio/sysbuild.cmake
@@ -20,6 +20,7 @@ if(SB_CONFIG_NET_CORE_IMAGE_HCI_IPC)
 
 	set(${NET_APP}_EXTRA_CONF_FILE
 	 ${APP_DIR}/overlay-nrf5340_cpunet_iso-bt_ll_sw_split.conf
+	 ${NET_APP_SRC_DIR}/debug_overlay.conf
 	 CACHE INTERNAL ""
 	)