diff --git a/openbsc/src/libbsc/bsc_vty.c b/openbsc/src/libbsc/bsc_vty.c
index cc46865..e81308b 100644
--- a/openbsc/src/libbsc/bsc_vty.c
+++ b/openbsc/src/libbsc/bsc_vty.c
@@ -2789,15 +2789,19 @@
 			VTY_NEWLINE);
 		return CMD_WARNING;
 	}
+	if (si2q_size_check(bts)) {
+		if (e->thresh_hi && thresh != e->thresh_hi)
+			vty_out(vty, "Warning: multiple thresholds are not "
+				"supported, overriding previous threshold %u%s",
+				e->thresh_hi, VTY_NEWLINE);
 
-	if (e->thresh_hi && thresh != e->thresh_hi)
-		vty_out(vty, "Warning: multiple thresholds are not supported, "
-			"overriding previous threshold %u%s",
-			e->thresh_hi, VTY_NEWLINE);
-
-	e->thresh_hi = thresh;
-
-	return CMD_SUCCESS;
+		e->thresh_hi = thresh;
+		return CMD_SUCCESS;
+	}
+	vty_out(vty, "Warning: not enough space in si2quater for a given arfcn%s"
+		, VTY_NEWLINE);
+	osmo_earfcn_del(e, arfcn);
+	return CMD_WARNING;
 }
 
 DEFUN(cfg_bts_si2quater_neigh_del, cfg_bts_si2quater_neigh_del_cmd,
@@ -2835,6 +2839,9 @@
 	case -ENOMEM:
 		vty_out(vty, "Unable to add arfcn: max number of UARFCNs (%u) "
 			"reached%s", MAX_EARFCN_LIST, VTY_NEWLINE);
+	case -ENOSPC:
+		vty_out(vty, "Warning: not enough space in si2quater for a "
+			"given arfcn%s", VTY_NEWLINE);
 	case -EADDRINUSE:
 		vty_out(vty, "Unable to add arfcn: (%u, %u) is already added%s",
 			arfcn, scramble, VTY_NEWLINE);
diff --git a/openbsc/src/libbsc/system_information.c b/openbsc/src/libbsc/system_information.c
index 8952534..3b0f889 100644
--- a/openbsc/src/libbsc/system_information.c
+++ b/openbsc/src/libbsc/system_information.c
@@ -134,6 +134,20 @@
 	return 29 + range1024_p(u_len);
 }
 
+bool si2q_size_check(const struct gsm_bts *bts)
+{
+	const struct osmo_earfcn_si2q *e = &bts->si_common.si2quater_neigh_list;
+	const uint16_t *u = bts->si_common.data.uarfcn_list,
+		*sc = bts->si_common.data.scramble_list;
+	size_t len = bts->si_common.uarfcn_length;
+	unsigned e_sz = e ? earfcn_size(e) : 1,
+		u_sz = len ? uarfcn_size(u, sc, len) : 1;
+	/* 2 bits are used in between UARFCN and EARFCN structs */
+	if (SI2Q_MIN_LEN + u_sz + 2 + e_sz > SI2Q_MAX_LEN)
+		return false;
+	return true;
+}
+
 /* 3GPP TS 44.018, Table 9.1.54.1 - prepend diversity bit to scrambling code */
 uint16_t encode_fdd(uint16_t scramble, bool diversity)
 {
@@ -198,7 +212,12 @@
 	ual[k] = arfcn;
 	scl[k] = scr;
 	bts->si_common.uarfcn_length++;
-	return 0;
+
+	if (si2q_size_check(bts))
+		return 0;
+
+	bts_uarfcn_del(bts, arfcn, scramble);
+	return -ENOSPC;
 }
 
 static inline int use_arfcn(const struct gsm_bts *bts, const bool bis, const bool ter,