diff --git a/include/osmocom/core/fsm.h b/include/osmocom/core/fsm.h
index 77ebe7c..5e5b091 100644
--- a/include/osmocom/core/fsm.h
+++ b/include/osmocom/core/fsm.h
@@ -224,9 +224,9 @@
 int osmo_fsm_inst_update_id_f(struct osmo_fsm_inst *fi, const char *fmt, ...);
 int osmo_fsm_inst_update_id_f_sanitize(struct osmo_fsm_inst *fi, char replace_with, const char *fmt, ...);
 
-const char *osmo_fsm_event_name(struct osmo_fsm *fsm, uint32_t event);
-const char *osmo_fsm_inst_name(struct osmo_fsm_inst *fi);
-const char *osmo_fsm_state_name(struct osmo_fsm *fsm, uint32_t state);
+const char *osmo_fsm_event_name(const struct osmo_fsm *fsm, uint32_t event);
+const char *osmo_fsm_inst_name(const struct osmo_fsm_inst *fi);
+const char *osmo_fsm_state_name(const struct osmo_fsm *fsm, uint32_t state);
 
 /*! return the name of the state the FSM instance is currently in. */
 static inline const char *osmo_fsm_inst_state_name(struct osmo_fsm_inst *fi)
diff --git a/src/fsm.c b/src/fsm.c
index b51c5cb..9333cac 100644
--- a/src/fsm.c
+++ b/src/fsm.c
@@ -576,7 +576,7 @@
  *  \param[in] event Event integer value
  *  \returns string rendering of the event
  */
-const char *osmo_fsm_event_name(struct osmo_fsm *fsm, uint32_t event)
+const char *osmo_fsm_event_name(const struct osmo_fsm *fsm, uint32_t event)
 {
 	static __thread char buf[32];
 	if (!fsm->event_names) {
@@ -590,7 +590,7 @@
  *  \param[in] fi FSM instance
  *  \returns string rendering of the FSM identity
  */
-const char *osmo_fsm_inst_name(struct osmo_fsm_inst *fi)
+const char *osmo_fsm_inst_name(const struct osmo_fsm_inst *fi)
 {
 	if (!fi)
 		return "NULL";
@@ -606,7 +606,7 @@
  *  \param[in] state FSM state number
  *  \returns string rendering of the FSM state
  */
-const char *osmo_fsm_state_name(struct osmo_fsm *fsm, uint32_t state)
+const char *osmo_fsm_state_name(const struct osmo_fsm *fsm, uint32_t state)
 {
 	static __thread char buf[32];
 	if (state >= fsm->num_states) {