diff --git a/openbsc/src/abis_nm.c b/openbsc/src/abis_nm.c
index 9ed7253..17e8d0f 100644
--- a/openbsc/src/abis_nm.c
+++ b/openbsc/src/abis_nm.c
@@ -1307,6 +1307,7 @@
 		if (len != IPACC_SEGMENT_SIZE)
 			sw->last_seg = 1;
 
+		++sw->seg_in_window;
 		msgb_tl16v_put(msg, NM_ATT_IPACC_FILE_DATA, len, (const u_int8_t *) seg_buf);
 		len += 3;
 		break;