diff --git a/src/Makefile b/src/Makefile
index 97239b5..67e6e98 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -38,7 +38,7 @@
 ranap/libosmo-asn1-ranap.a:
 	$(MAKE) -C ranap
 
-hnbgw: asn1helpers.o hnbgw.o hnbgw_hnbap.o hnbgw_rua.o hnbgw_ranap.o $(HNBAP_OBJS) $(RUA_OBJS) $(RANAP_OBJS) $(LIBS)
+hnbgw: iu_helpers.o asn1helpers.o hnbgw.o hnbgw_hnbap.o hnbgw_rua.o hnbgw_ranap.o $(HNBAP_OBJS) $(RUA_OBJS) $(RANAP_OBJS) $(LIBS)
 	$(CC) $(LDFLAGS) -o $@ $^
 
 %.o: %.c
diff --git a/src/hnbgw_hnbap.c b/src/hnbgw_hnbap.c
index 8b1527e..1915ad6 100644
--- a/src/hnbgw_hnbap.c
+++ b/src/hnbgw_hnbap.c
@@ -24,52 +24,6 @@
 	return osmo_wqueue_enqueue(&ctx->wqueue, msg);
 }
 
-int decode_iu_bcd(char *out, size_t out_len, const uint8_t *in, size_t in_len)
-{
-	const uint8_t *ch;
-	char *outch = out;
-
-	for (ch = in; ch < in + in_len; ch++) {
-		char c = osmo_bcd2char(*ch & 0xF);
-		*outch++ = c;
-		if (outch + 1 >= out + out_len)
-			break;
-		c = osmo_bcd2char(*ch >> 4);
-		/* skip padding nibble at end */
-		if (c == 'F')
-			break;
-		*outch++ = c;
-	}
-	*outch++ = '\0';
-	return outch - out;
-}
-
-int encode_iu_imsi(uint8_t *out, size_t out_len,
-		   const char *in)
-{
-	unsigned int len = strlen(in);
-	uint8_t odd = (len & 0x01) == 1;
-	unsigned int off = 0;
-	unsigned int i;
-
-	len /= 2;
-	if (odd)
-		len++;
-
-	for (i = 0; i < len; i++) {
-		uint8_t lower, upper;
-
-		lower = osmo_char2bcd(in[++off]) & 0x0f;
-		if (!odd && off + 1 == len)
-			upper = 0x0f;
-		else
-			upper = osmo_char2bcd(in[++off]) & 0x0f;
-
-		out[i] = (upper << 4) | lower;
-	}
-	return i;
-}
-
 static int hnbgw_tx_hnb_register_acc(struct hnb_context *ctx)
 {
 	HNBRegisterAccept_t accept_out;
diff --git a/src/iu_helpers.c b/src/iu_helpers.c
new file mode 100644
index 0000000..5064665
--- /dev/null
+++ b/src/iu_helpers.c
@@ -0,0 +1,48 @@
+#include <stdint.h>
+
+#include <osmocom/core/utils.h>
+
+int decode_iu_bcd(char *out, size_t out_len, const uint8_t *in, size_t in_len)
+{
+	const uint8_t *ch;
+	char *outch = out;
+
+	for (ch = in; ch < in + in_len; ch++) {
+		char c = osmo_bcd2char(*ch & 0xF);
+		*outch++ = c;
+		if (outch + 1 >= out + out_len)
+			break;
+		c = osmo_bcd2char(*ch >> 4);
+		/* skip padding nibble at end */
+		if (c == 'F')
+			break;
+		*outch++ = c;
+	}
+	*outch++ = '\0';
+	return outch - out;
+}
+
+int encode_iu_imsi(uint8_t *out, size_t out_len, const char *in)
+{
+	unsigned int len = strlen(in);
+	uint8_t odd = (len & 0x01) == 1;
+	unsigned int off = 0;
+	unsigned int i;
+
+	len /= 2;
+	if (odd)
+		len++;
+
+	for (i = 0; i < len; i++) {
+		uint8_t lower, upper;
+
+		lower = osmo_char2bcd(in[++off]) & 0x0f;
+		if (!odd && off + 1 == len)
+			upper = 0x0f;
+		else
+			upper = osmo_char2bcd(in[++off]) & 0x0f;
+
+		out[i] = (upper << 4) | lower;
+	}
+	return i;
+}
diff --git a/src/iu_helpers.h b/src/iu_helpers.h
new file mode 100644
index 0000000..4733bbc
--- /dev/null
+++ b/src/iu_helpers.h
@@ -0,0 +1,6 @@
+#pragma once
+
+#include <stdint.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);