diff --git a/src/box/box.cc b/src/box/box.cc
index bfef966fd..1decb956a 100644
--- a/src/box/box.cc
+++ b/src/box/box.cc
@@ -1879,16 +1879,24 @@ box_wait_limbo_acked(double timeout)
        last_entry = txn_limbo_last_synchro_entry(&txn_limbo);
        /* Wait for the last entries WAL write. */
        if (last_entry->lsn < 0) {
+               assert(false);
                int64_t tid = last_entry->txn->id;

-               if (wal_sync(NULL) != 0)
+               if (wal_sync(NULL) != 0) {
+                       assert(false);
                        return -1;
+               }

-               if (box_check_promote_term_intact(promote_term) != 0)
+               if (box_check_promote_term_intact(promote_term) != 0) {
+                       assert(false);
                        return -1;
-               if (txn_limbo_is_empty(&txn_limbo))
+               }
+               if (txn_limbo_is_empty(&txn_limbo)) {
+                       assert(false);
                        return txn_limbo.confirmed_lsn;
+               }
                if (tid != txn_limbo_last_synchro_entry(&txn_limbo)->txn->id) {
+                       assert(false);
                        diag_set(ClientError, ER_QUORUM_WAIT, quorum,
                                 "new synchronous transactions appeared");
                        return -1;
@@ -1900,18 +1908,24 @@ box_wait_limbo_acked(double timeout)
        if (box_wait_quorum(txn_limbo.owner_id, wait_lsn, quorum, timeout) != 0)
                return -1;

-       if (box_check_promote_term_intact(promote_term) != 0)
+       if (box_check_promote_term_intact(promote_term) != 0) {
+               assert(false);
                return -1;
+       }

-       if (txn_limbo_is_empty(&txn_limbo))
+       if (txn_limbo_is_empty(&txn_limbo)) {
+               assert(false);
                return txn_limbo.confirmed_lsn;
+       }

        if (quorum < replication_synchro_quorum) {
+               assert(false);
                diag_set(ClientError, ER_QUORUM_WAIT, quorum,
                         "quorum was increased while waiting");
                return -1;
        }
        if (wait_lsn < txn_limbo_last_synchro_entry(&txn_limbo)->lsn) {
+               assert(false);
                diag_set(ClientError, ER_QUORUM_WAIT, quorum,
                         "new synchronous transactions appeared");
                return -1;