diff --git a/include/osmocom/sgsn/Makefile.am b/include/osmocom/sgsn/Makefile.am
index 3f63b9f..269cebc 100644
--- a/include/osmocom/sgsn/Makefile.am
+++ b/include/osmocom/sgsn/Makefile.am
@@ -17,7 +17,6 @@
 	gprs_utils.h \
 	gsup_client.h \
 	gtphub.h \
-	oap_client.h \
 	sgsn.h \
 	signal.h \
 	slhc.h \
diff --git a/include/osmocom/sgsn/gsup_client.h b/include/osmocom/sgsn/gsup_client.h
index 29092ad..6ba0d15 100644
--- a/include/osmocom/sgsn/gsup_client.h
+++ b/include/osmocom/sgsn/gsup_client.h
@@ -23,7 +23,7 @@
 
 #include <osmocom/core/timer.h>
 
-#include <osmocom/sgsn/oap_client.h>
+#include <osmocom/gsm/oap_client.h>
 
 #define GSUP_CLIENT_RECONNECT_INTERVAL 10
 #define GSUP_CLIENT_PING_INTERVAL 20
@@ -43,7 +43,7 @@
 	gsup_client_read_cb_t read_cb;
 	void *data;
 
-	struct oap_client_state oap_state;
+	struct osmo_oap_client_state oap_state;
 
 	struct osmo_timer_list ping_timer;
 	struct osmo_timer_list connect_timer;
@@ -55,7 +55,7 @@
 				       const char *ip_addr,
 				       unsigned int tcp_port,
 				       gsup_client_read_cb_t read_cb,
-				       struct oap_client_config *oapc_config);
+				       struct osmo_oap_client_config *oapc_config);
 
 void gsup_client_destroy(struct gsup_client *gsupc);
 int gsup_client_send(struct gsup_client *gsupc, struct msgb *msg);
diff --git a/include/osmocom/sgsn/oap_client.h b/include/osmocom/sgsn/oap_client.h
deleted file mode 100644
index 80c86d5..0000000
--- a/include/osmocom/sgsn/oap_client.h
+++ /dev/null
@@ -1,82 +0,0 @@
-/* Osmocom Authentication Protocol API */
-
-/* (C) 2015 by Sysmocom s.f.m.c. GmbH
- * All Rights Reserved
- *
- * Author: Neels Hofmeyr
- *
- * 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/>.
- *
- */
-
-#pragma once
-
-#include <stdint.h>
-
-struct msgb;
-struct osmo_oap_message;
-
-/* This is the config part for vty. It is essentially copied in
- * oap_client_state, where values are copied over once the config is
- * considered valid. */
-struct oap_client_config {
-	uint16_t client_id;
-	int secret_k_present;
-	uint8_t secret_k[16];
-	int secret_opc_present;
-	uint8_t secret_opc[16];
-};
-
-/* The runtime state of the OAP client. client_id and the secrets are in fact
- * duplicated from oap_client_config, so that a separate validation of the
- * config data is possible, and so that only a struct oap_client_state* is
- * passed around. */
-struct oap_client_state {
-	enum {
-		OAP_UNINITIALIZED = 0,	/* just allocated. */
-		OAP_DISABLED,		/* disabled by config. */
-		OAP_INITIALIZED,	/* enabled, config is valid. */
-		OAP_REQUESTED_CHALLENGE,
-		OAP_SENT_CHALLENGE_RESULT,
-		OAP_REGISTERED
-	} state;
-	uint16_t client_id;
-	uint8_t secret_k[16];
-	uint8_t secret_opc[16];
-	int registration_failures;
-};
-
-/* From config, initialize state. Return 0 on success. */
-int oap_client_init(struct oap_client_config *config,
-		    struct oap_client_state *state);
-
-/* Construct an OAP registration message and return in *msg_tx. Use
- * state->client_id and update state->state.
- * Return 0 on success, or a negative value on error.
- * If an error is returned, *msg_tx is guaranteed to be NULL. */
-int oap_client_register(struct oap_client_state *state, struct msgb **msg_tx);
-
-/* Decode and act on a received OAP message msg_rx. Update state->state.  If a
- * non-NULL pointer is returned in *msg_tx, that msgb should be sent to the OAP
- * server (and freed) by the caller. The received msg_rx is not freed.
- * Return 0 on success, or a negative value on error.
- * If an error is returned, *msg_tx is guaranteed to be NULL. */
-int oap_client_handle(struct oap_client_state *state,
-		      const struct msgb *msg_rx, struct msgb **msg_tx);
-
-/* Allocate a msgb and in it, return the encoded oap_client_msg. Return
- * NULL on error. (Like oap_client_encode(), but also allocates a msgb.)
- * About the name: the idea is do_something(oap_client_encoded(my_struct))
- */
-struct msgb *oap_client_encoded(const struct osmo_oap_message *oap_client_msg);
diff --git a/include/osmocom/sgsn/sgsn.h b/include/osmocom/sgsn/sgsn.h
index dae9d12..59d0bd7 100644
--- a/include/osmocom/sgsn/sgsn.h
+++ b/include/osmocom/sgsn/sgsn.h
@@ -6,7 +6,7 @@
 #include <osmocom/crypt/gprs_cipher.h>
 #include <osmocom/gprs/gprs_ns.h>
 #include <osmocom/sgsn/gprs_sgsn.h>
-#include <osmocom/sgsn/oap_client.h>
+#include <osmocom/gsm/oap_client.h>
 #include <osmocom/sgsn/common.h>
 
 #include "../../bscconfig.h"
@@ -101,7 +101,7 @@
 
 	int dynamic_lookup;
 
-	struct oap_client_config oap;
+	struct osmo_oap_client_config oap;
 
 	/* RFC1144 TCP/IP header compression */
 	struct {