diff --git a/include/osmocom/core/fsm.h b/include/osmocom/core/fsm.h
index 5e5b091c4..a1ffd30dc 100644
--- a/include/osmocom/core/fsm.h
+++ b/include/osmocom/core/fsm.h
@@ -200,7 +200,7 @@ void osmo_fsm_set_dealloc_ctx(void *ctx);
 			    fmt, ## args)
 
 #define OSMO_T_FMT "%c%u"
-#define OSMO_T_FMT_ARGS(T) ((T) >= 0 ? 'T' : 'X'), ((T) >= 0 ? T : -T)
+#define OSMO_T_FMT_ARGS(T) ((T) >= 0 ? 'T' : 'X'), ((T) >= 0 ? (T) : -(T))
 
 int osmo_fsm_register(struct osmo_fsm *fsm);
 void osmo_fsm_unregister(struct osmo_fsm *fsm);