diff --git a/include/osmocom/core/tdef.h b/include/osmocom/core/tdef.h
index a1ad4cc..8155688 100644
--- a/include/osmocom/core/tdef.h
+++ b/include/osmocom/core/tdef.h
@@ -97,7 +97,7 @@
 unsigned long osmo_tdef_get(const struct osmo_tdef *tdefs, int T, enum osmo_tdef_unit as_unit,
 			    long val_if_not_present);
 struct osmo_tdef *osmo_tdef_get_entry(struct osmo_tdef *tdefs, int T);
-int osmo_tdef_set(struct osmo_tdef *tdefs, int T, unsigned long val, enum osmo_tdef_unit as_unit);
+int osmo_tdef_set(struct osmo_tdef *tdefs, int T, unsigned long val, enum osmo_tdef_unit val_unit);
 
 /*! Using osmo_tdef for osmo_fsm_inst: array entry for a mapping of state numbers to timeout definitions.
  * For a usage example, see osmo_tdef_get_state_timeout() and test_tdef_state_timeout() in tdef_test.c. */