diff --git a/src/libmsc/iu_dummy.c b/src/libmsc/iu_dummy.c
new file mode 100644
index 0000000..1f5dffb
--- /dev/null
+++ b/src/libmsc/iu_dummy.c
@@ -0,0 +1,93 @@
+/* Trivial switch-off of external Iu dependencies,
+ * allowing to run full unit tests even when built without Iu support. */
+
+/*
+ * (C) 2016,2017 by sysmocom s.f.m.c. GmbH <info@sysmocom.de>
+ *
+ * Author: Neels Hofmeyr <nhofmeyr@sysmocom.de>
+ *
+ * All Rights Reserved
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#include "../../bscconfig.h"
+#ifndef BUILD_IU
+
+#include <stdint.h>
+#include <stdbool.h>
+
+#include <osmocom/core/logging.h>
+#include <osmocom/vty/logging.h>
+#include <osmocom/core/msgb.h>
+
+struct msgb;
+struct ue_conn_ctx;
+struct gsm_auth_tuple;
+struct RANAP_Cause;
+
+int iu_tx(struct msgb *msg, uint8_t sapi)
+{
+	LOGP(DLGLOBAL, LOGL_INFO, "iu_tx() dummy called, NOT transmitting %d bytes: %s\n",
+	     msg->len, osmo_hexdump(msg->data, msg->len));
+	return 0;
+}
+
+int iu_tx_sec_mode_cmd(struct ue_conn_ctx *uectx, struct gsm_auth_tuple *tp,
+		       int send_ck)
+{
+	LOGP(DLGLOBAL, LOGL_INFO, "iu_tx_sec_mode_cmd() dummy called, NOT transmitting Security Mode Command\n");
+	return 0;
+}
+
+int iu_page_cs(const char *imsi, const uint32_t *tmsi, uint16_t lac)
+{
+	LOGP(DLGLOBAL, LOGL_INFO, "iu_page_cs() dummy called, NOT paging\n");
+	return 23;
+}
+
+int iu_page_ps(const char *imsi, const uint32_t *ptmsi, uint16_t lac, uint8_t rac)
+{
+	LOGP(DLGLOBAL, LOGL_INFO, "iu_page_ps() dummy called, NOT paging\n");
+	return 0;
+}
+
+struct msgb *ranap_new_msg_rab_assign_voice(uint8_t rab_id, uint32_t rtp_ip,
+					    uint16_t rtp_port,
+					    bool use_x213_nsap)
+{
+	LOGP(DLGLOBAL, LOGL_INFO, "ranap_new_msg_rab_assign_voice() dummy called, NOT composing RAB Assignment\n");
+	return NULL;
+}
+
+int iu_rab_act(struct ue_conn_ctx *ue_ctx, struct msgb *msg)
+{
+	LOGP(DLGLOBAL, LOGL_INFO, "iu_rab_act() dummy called, NOT activating RAB\n");
+	return 0;
+}
+
+int iu_tx_common_id(struct ue_conn_ctx *uectx, const char *imsi)
+{
+	LOGP(DLGLOBAL, LOGL_INFO, "iu_tx_common_id() dummy called, NOT sending CommonID\n");
+	return 0;
+}
+
+int iu_tx_release(struct ue_conn_ctx *ctx, const struct RANAP_Cause *cause)
+{
+	LOGP(DLGLOBAL, LOGL_INFO, "iu_tx_release() dummy called, NOT sending Release\n");
+	return 0;
+}
+
+#endif