diff --git a/src/gprs_rlcmac_ts_alloc.cpp b/src/gprs_rlcmac_ts_alloc.cpp
index 836dab5..496d19b 100644
--- a/src/gprs_rlcmac_ts_alloc.cpp
+++ b/src/gprs_rlcmac_ts_alloc.cpp
@@ -896,8 +896,6 @@
 	if (rc < 0)
 		return -EINVAL;
 
-	first_ts = ffs(rc) - 1;
-
 	/* Step 3b: Derive the slot set for a given direction */
 	if (tbf->direction == GPRS_RLCMAC_DL_TBF) {
 		dl_slots = rc;
@@ -914,6 +912,7 @@
 		update_slot_counters(ul_slots, reserved_ul_slots, &slotcount, &avail_count);
 	}
 
+	first_ts = ffs(rc) - 1;
 	first_common_ts = ffs(dl_slots & ul_slots) - 1;
 
 	if (first_common_ts < 0) {