diff --git a/driver/src/main/java/oracle/nosql/driver/ops/serde/nson/NsonSerializerFactory.java b/driver/src/main/java/oracle/nosql/driver/ops/serde/nson/NsonSerializerFactory.java
index de2a0118..fb791aab 100644
--- a/driver/src/main/java/oracle/nosql/driver/ops/serde/nson/NsonSerializerFactory.java
+++ b/driver/src/main/java/oracle/nosql/driver/ops/serde/nson/NsonSerializerFactory.java
@@ -2670,7 +2670,7 @@ static void readTopologyInfo(ByteInputStream in,
                                              Result result)
             throws IOException {
 
-            int proxyTopoSeqNum = 1;
+            int proxyTopoSeqNum = -1;
             int[] shardIds = null;
             MapWalker walker = new MapWalker(in);
 
diff --git a/driver/src/main/java/oracle/nosql/driver/query/TopologyInfo.java b/driver/src/main/java/oracle/nosql/driver/query/TopologyInfo.java
index 28665ebc..3cb11f20 100644
--- a/driver/src/main/java/oracle/nosql/driver/query/TopologyInfo.java
+++ b/driver/src/main/java/oracle/nosql/driver/query/TopologyInfo.java
@@ -16,6 +16,9 @@ public class TopologyInfo {
     private int[] theShardIds;
 
     public TopologyInfo(int seqNum, int[] shardIds) {
+        if (shardIds == null) {
+            throw new IllegalArgumentException("TopologyInfo shardIds must not be null");
+        }
         theSeqNum = seqNum;
         theShardIds = shardIds;
     }