diff --git a/asterixdb/asterix-app/src/main/java/org/apache/asterix/api/http/server/NCQueryServiceServlet.java b/asterixdb/asterix-app/src/main/java/org/apache/asterix/api/http/server/NCQueryServiceServlet.java
index 55f3369..d9b69cb 100644
--- a/asterixdb/asterix-app/src/main/java/org/apache/asterix/api/http/server/NCQueryServiceServlet.java
+++ b/asterixdb/asterix-app/src/main/java/org/apache/asterix/api/http/server/NCQueryServiceServlet.java
@@ -136,6 +136,9 @@
 
     private void cancelQuery(INCMessageBroker messageBroker, String nodeId, String clientContextID, Exception exception,
             boolean wait) {
+        if (clientContextID == null) {
+            return;
+        }
         MessageFuture cancelQueryFuture = messageBroker.registerMessageFuture();
         try {
             CancelQueryRequest cancelQueryMessage =
diff --git a/asterixdb/asterix-runtime/src/main/java/org/apache/asterix/runtime/utils/RequestTracker.java b/asterixdb/asterix-runtime/src/main/java/org/apache/asterix/runtime/utils/RequestTracker.java
index f651eb36..a0ab559 100644
--- a/asterixdb/asterix-runtime/src/main/java/org/apache/asterix/runtime/utils/RequestTracker.java
+++ b/asterixdb/asterix-runtime/src/main/java/org/apache/asterix/runtime/utils/RequestTracker.java
@@ -21,6 +21,7 @@
 import java.util.Collection;
 import java.util.Collections;
 import java.util.Map;
+import java.util.Objects;
 import java.util.concurrent.ConcurrentHashMap;
 
 import org.apache.asterix.common.api.IClientRequest;
@@ -45,6 +46,7 @@
 
     @Override
     public IClientRequest getByClientContextId(String clientContextId) {
+        Objects.requireNonNull(clientContextId, "clientContextId must not be null");
         return clientIdRequests.get(clientContextId);
     }