diff --git a/src/Makefile.am b/src/Makefile.am
index 93b6fba..6dbd73e 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -24,9 +24,9 @@
 lib_LTLIBRARIES = libosmo-ranap.la
 libosmo_ranap_la_LDFLAGS = $(AM_LDFLAGS) -version-info $(RANAP_LIBVERSION)
 libosmo_ranap_la_LIBADD = $(OSMOCORE_LIBS) $(OSMOGSM_LIBS) $(ASN1C_LIBS) $(COMMON_LDADD) ranap/libosmo-asn1-ranap.la
-libosmo_ranap_la_SOURCES = ranap_common.c ranap_encoder.c ranap_decoder.c ranap_msg_factory.c
+libosmo_ranap_la_SOURCES = ranap_common.c ranap_encoder.c ranap_decoder.c ranap_msg_factory.c iu_helpers.c
 
-osmoranap_HEADERS = ranap_common.h ranap_ies_defs.h ranap_msg_factory.h
+osmoranap_HEADERS = ranap_common.h ranap_ies_defs.h ranap_msg_factory.h iu_helpers.h
 osmoranapdir = $(includedir)/osmocom/ranap
 
 
@@ -41,7 +41,7 @@
 
 osmo_hnbgw_SOURCES = hnbap_encoder.c hnbap_decoder.c hnbap_common.c \
 		     rua_encoder.c rua_decoder.c rua_common.c \
-		     iu_helpers.c asn1helpers.c sccp_helpers.c \
+		     asn1helpers.c sccp_helpers.c \
 		     hnbgw.c hnbgw_hnbap.c hnbgw_rua.c hnbgw_ranap.c \
 		     context_map.c hnbgw_cn.c
 
diff --git a/src/hnbgw_hnbap.c b/src/hnbgw_hnbap.c
index 87dc343..7790bfd 100644
--- a/src/hnbgw_hnbap.c
+++ b/src/hnbgw_hnbap.c
@@ -86,7 +86,7 @@
 	size_t encoded_imsi_len;
 	int rc;
 
-	encoded_imsi_len = encode_iu_imsi(encoded_imsi,
+	encoded_imsi_len = ranap_imsi_encode(encoded_imsi,
 					  sizeof(encoded_imsi), ue->imsi);
 
 	memset(&accept, 0, sizeof(accept));
@@ -150,15 +150,15 @@
 
 	switch (ies.uE_Identity.present) {
 	case UE_Identity_PR_iMSI:
-		decode_iu_bcd(imsi, sizeof(imsi), ies.uE_Identity.choice.iMSI.buf,
+		ranap_bcd_decode(imsi, sizeof(imsi), ies.uE_Identity.choice.iMSI.buf,
 			      ies.uE_Identity.choice.iMSI.size);
 		break;
 	case UE_Identity_PR_iMSIDS41:
-		decode_iu_bcd(imsi, sizeof(imsi), ies.uE_Identity.choice.iMSIDS41.buf,
+		ranap_bcd_decode(imsi, sizeof(imsi), ies.uE_Identity.choice.iMSIDS41.buf,
 			      ies.uE_Identity.choice.iMSIDS41.size);
 		break;
 	case UE_Identity_PR_iMSIESN:
-		decode_iu_bcd(imsi, sizeof(imsi), ies.uE_Identity.choice.iMSIESN.iMSIDS41.buf,
+		ranap_bcd_decode(imsi, sizeof(imsi), ies.uE_Identity.choice.iMSIESN.iMSIDS41.buf,
 			      ies.uE_Identity.choice.iMSIESN.iMSIDS41.size);
 		break;
 	default:
diff --git a/src/iu_helpers.c b/src/iu_helpers.c
index dfe47d6..2f44e93 100644
--- a/src/iu_helpers.c
+++ b/src/iu_helpers.c
@@ -24,7 +24,7 @@
 #include <osmocom/core/utils.h>
 
 /* decode a BCD-string as used inside ASN.1 encoded Iu interface protocols */
-int decode_iu_bcd(char *out, size_t out_len, const uint8_t *in, size_t in_len)
+int ranap_bcd_decode(char *out, size_t out_len, const uint8_t *in, size_t in_len)
 {
 	const uint8_t *ch;
 	char *outch = out;
@@ -45,7 +45,7 @@
 }
 
 /* decode an IMSI as used inside ASN.1 encoded Iu interface protocols */
-int encode_iu_imsi(uint8_t *out, size_t out_len, const char *in)
+int ranap_imsi_encode(uint8_t *out, size_t out_len, const char *in)
 {
 	unsigned int len = strlen(in);
 	unsigned int octlen;
diff --git a/src/iu_helpers.h b/src/iu_helpers.h
index 531d673..109b6da 100644
--- a/src/iu_helpers.h
+++ b/src/iu_helpers.h
@@ -3,5 +3,5 @@
 #include <stdint.h>
 #include <sys/types.h>
 
-int decode_iu_bcd(char *out, size_t out_len, const uint8_t *in, size_t in_len);
-int encode_iu_imsi(uint8_t *out, size_t out_len, const char *in);
+int ranap_bcd_decode(char *out, size_t out_len, const uint8_t *in, size_t in_len);
+int ranap_imsi_encode(uint8_t *out, size_t out_len, const char *in);
diff --git a/src/ranap_msg_factory.c b/src/ranap_msg_factory.c
index 3e69c48..0c015e5 100644
--- a/src/ranap_msg_factory.c
+++ b/src/ranap_msg_factory.c
@@ -276,7 +276,7 @@
 
 	if (imsi) {
 		uint8_t *imsi_buf = CALLOC(1, 16);
-		rc = encode_iu_imsi(imsi_buf, 16, imsi);
+		rc = ranap_imsi_encode(imsi_buf, 16, imsi);
 		ies.permanentNAS_UE_ID.present = RANAP_PermanentNAS_UE_ID_PR_iMSI;
 		ies.permanentNAS_UE_ID.choice.iMSI.buf = imsi_buf;
 		ies.permanentNAS_UE_ID.choice.iMSI.size = rc;
@@ -350,7 +350,7 @@
 	else
 		ies.cN_DomainIndicator = RANAP_CN_DomainIndicator_cs_domain;
 
-	rc = encode_iu_imsi(imsi_buf, 16, imsi);
+	rc = ranap_imsi_encode(imsi_buf, 16, imsi);
 	ies.permanentNAS_UE_ID.present = RANAP_PermanentNAS_UE_ID_PR_iMSI;
 	ies.permanentNAS_UE_ID.choice.iMSI.buf = imsi_buf;
 	ies.permanentNAS_UE_ID.choice.iMSI.size = rc;
diff --git a/src/tests/Makefile.am b/src/tests/Makefile.am
index 973cf3f..43b63cc 100644
--- a/src/tests/Makefile.am
+++ b/src/tests/Makefile.am
@@ -6,13 +6,13 @@
 
 HNBAP_FILES = $(top_builddir)/src/hnbap_common.c $(top_builddir)/src/hnbap_decoder.c $(top_builddir)/src/hnbap_encoder.c
 RUA_FILES = $(top_builddir)/src/rua_common.c $(top_builddir)/src/rua_decoder.c $(top_builddir)/src/rua_encoder.c
-HELPER_FILES = $(top_builddir)/src/iu_helpers.c $(top_builddir)/src/asn1helpers.c
+HELPER_FILES = $(top_builddir)/src/asn1helpers.c
 
 test_helpers_SOURCES = $(HELPER_FILES) test-helpers.c
-test_helpers_LDADD = $(COMMON_LIBS)
+test_helpers_LDADD = $(COMMON_LIBS) $(top_builddir)/src/libosmo-ranap.la
 
 test_hnbap_SOURCES = $(HELPER_FILES) $(top_builddir)/src/hnbap_common.c $(top_builddir)/src/hnbap_decoder.c test-hnbap.c test_common.c
-test_hnbap_LDADD = $(COMMON_LIBS) $(top_builddir)/src/hnbap/libosmo-asn1-hnbap.a
+test_hnbap_LDADD = $(COMMON_LIBS) $(top_builddir)/src/hnbap/libosmo-asn1-hnbap.a $(top_builddir)/src/libosmo-ranap.la
 
 hnb_test_SOURCES = $(HELPER_FILES) $(HNBAP_FILES) $(RUA_FILES) hnb-test.c rua_helper.c test_common.c
 hnb_test_LDADD = $(COMMON_LIBS) $(top_builddir)/src/hnbap/libosmo-asn1-hnbap.a $(top_builddir)/src/rua/libosmo-asn1-rua.a $(top_builddir)/src/libosmo-ranap.la
diff --git a/src/tests/hnb-test.c b/src/tests/hnb-test.c
index cd07d7c..f26e222 100644
--- a/src/tests/hnb-test.c
+++ b/src/tests/hnb-test.c
@@ -106,7 +106,7 @@
 
 	request.uE_Identity.present = UE_Identity_PR_iMSI;
 
-	imsi_len = encode_iu_imsi(imsi_buf, sizeof(imsi_buf), imsi_str);
+	imsi_len = ranap_imsi_encode(imsi_buf, sizeof(imsi_buf), imsi_str);
 	OCTET_STRING_fromBuf(&request.uE_Identity.choice.iMSI, imsi_buf, imsi_len);
 
 	request.registration_Cause = Registration_Cause_normal;
@@ -162,7 +162,7 @@
 
 	ctx_id = asn1bitstr_to_u24(&accept.context_ID);
 
-	decode_iu_bcd(imsi, sizeof(imsi), accept.uE_Identity.choice.iMSI.buf,
+	ranap_bcd_decode(imsi, sizeof(imsi), accept.uE_Identity.choice.iMSI.buf,
 			accept.uE_Identity.choice.iMSI.size);
 	printf("UE Register accept for IMSI %s, context %u\n", imsi, ctx_id);
 
diff --git a/src/tests/test-helpers.c b/src/tests/test-helpers.c
index 60f3d3b..b514d10 100644
--- a/src/tests/test-helpers.c
+++ b/src/tests/test-helpers.c
@@ -27,6 +27,7 @@
 
 #include <osmocom/core/utils.h>
 
+int asn1_xer_print = 0;
 void *talloc_asn1_ctx;
 
 /* use odd number of digits */
@@ -43,13 +44,13 @@
 
 	printf("pre-encoded: %s\n", osmo_hexdump_nospc(imsi_encoded,
 						sizeof(imsi_encoded)));
-	rc = decode_iu_bcd(outstr, sizeof(outstr), imsi_encoded,
+	rc = ranap_bcd_decode(outstr, sizeof(outstr), imsi_encoded,
 			   sizeof(imsi_encoded));
 	ASSERT(rc >= 0);
 	printf("decoded: %s\n", outstr);
 	ASSERT(!strcmp(outstr, imsi_decoded));
 
-	rc = encode_iu_imsi(outbuf, sizeof(outbuf), imsi_decoded);
+	rc = ranap_imsi_encode(outbuf, sizeof(outbuf), imsi_decoded);
 	ASSERT(rc >= 0);
 	printf("re-encoded: %s\n", osmo_hexdump_nospc(outbuf, rc));
 	ASSERT(!memcmp(outbuf, imsi_encoded, sizeof(imsi_encoded)));
diff --git a/src/tests/test-hnbap.c b/src/tests/test-hnbap.c
index 0005fe1..5101ff4 100644
--- a/src/tests/test-hnbap.c
+++ b/src/tests/test-hnbap.c
@@ -134,7 +134,7 @@
 	ASSERT(rc >= 0);
 
 	ASSERT(ue_req_ies.uE_Identity.present == UE_Identity_PR_iMSI);
-	decode_iu_bcd(imsi, sizeof(imsi), ue_req_ies.uE_Identity.choice.iMSI.buf,
+	ranap_bcd_decode(imsi, sizeof(imsi), ue_req_ies.uE_Identity.choice.iMSI.buf,
 			ue_req_ies.uE_Identity.choice.iMSI.size);
 
 	printf("HNBAP UE Register request from IMSI %s\n", imsi);
@@ -154,7 +154,7 @@
 	ASSERT(rc >= 0);
 
 	ASSERT(ue_acc_ies.uE_Identity.present == UE_Identity_PR_iMSI);
-	decode_iu_bcd(imsi, sizeof(imsi), ue_acc_ies.uE_Identity.choice.iMSI.buf,
+	ranap_bcd_decode(imsi, sizeof(imsi), ue_acc_ies.uE_Identity.choice.iMSI.buf,
 			ue_acc_ies.uE_Identity.choice.iMSI.size);
 
 	printf("HNBAP UE Register accept to IMSI %s\n", imsi);