diff --git a/include/osmocom/gsm/apn.h b/include/osmocom/gsm/apn.h
index 8d35324..288b229 100644
--- a/include/osmocom/gsm/apn.h
+++ b/include/osmocom/gsm/apn.h
@@ -18,4 +18,4 @@
 				 const char *ni, int have_3dig_mnc);
 
 int osmo_apn_from_str(uint8_t *apn_enc, size_t max_apn_enc_len, const char *str);
-char * osmo_apn_to_str(char *out_str, const uint8_t *apn_enc, size_t apn_enc_len);
+char *osmo_apn_to_str(char *out_str, const uint8_t *apn_enc, size_t apn_enc_len);