diff --git a/include/openbsc/abis_rsl.h b/include/openbsc/abis_rsl.h
index 420f3f4..1968671 100644
--- a/include/openbsc/abis_rsl.h
+++ b/include/openbsc/abis_rsl.h
@@ -376,6 +376,7 @@
 unsigned int get_paging_group(u_int64_t imsi, unsigned int bs_cc_chans,
 			      int n_pag_blocks);
 unsigned int n_pag_blocks(int bs_ccch_sdcch_comb, unsigned int bs_ag_blks_res);
+u_int64_t str_to_imsi(const char *imsi_str);
 
 /* to be provided by external code */
 int abis_rsl_sendmsg(struct msgb *msg);