diff --git a/src/tbf.cpp b/src/tbf.cpp
index 74c790ca..35bd81d0 100644
--- a/src/tbf.cpp
+++ b/src/tbf.cpp
@@ -544,7 +544,7 @@ void gprs_rlcmac_tbf::t_start(enum tbf_timers t, int T, const char *reason, bool
 }
 
 int gprs_rlcmac_tbf::check_polling(uint32_t fn, uint8_t ts,
-	uint32_t *poll_fn_, unsigned int *rrbp_)
+	uint32_t *poll_fn_, unsigned int *rrbp_) const
 {
 	uint32_t new_poll_fn = next_fn(fn, 13);
 
@@ -1066,7 +1066,7 @@ int gprs_rlcmac_tbf::establish_dl_tbf_on_pacch()
 	return 0;
 }
 
-const char *tbf_name(gprs_rlcmac_tbf *tbf)
+const char *tbf_name(const gprs_rlcmac_tbf *tbf)
 {
 	return tbf ? tbf->name() : "(no TBF)";
 }
diff --git a/src/tbf.h b/src/tbf.h
index a2c47477..1d28afbb 100644
--- a/src/tbf.h
+++ b/src/tbf.h
@@ -190,7 +190,7 @@ enum tbf_counters { /* TBF counters from 3GPP TS 44.060 §13.4 */
 extern "C" {
 #endif
 struct gprs_rlcmac_tbf;
-const char *tbf_name(struct gprs_rlcmac_tbf *tbf);
+const char *tbf_name(const struct gprs_rlcmac_tbf *tbf);
 enum gprs_rlcmac_tbf_state tbf_state(const struct gprs_rlcmac_tbf *tbf);
 enum gprs_rlcmac_tbf_direction tbf_direction(const struct gprs_rlcmac_tbf *tbf);
 void tbf_set_ms(struct gprs_rlcmac_tbf *tbf, struct GprsMs *ms);
@@ -262,7 +262,7 @@ struct gprs_rlcmac_tbf {
 	int establish_dl_tbf_on_pacch();
 
 	int check_polling(uint32_t fn, uint8_t ts,
-		uint32_t *poll_fn, unsigned int *rrbp);
+		uint32_t *poll_fn, unsigned int *rrbp) const;
 	void set_polling(uint32_t poll_fn, uint8_t ts, enum gprs_rlcmac_tbf_poll_type t);
 	void poll_timeout();