diff --git a/nifi-nar-bundles/nifi-redis-bundle/nifi-redis-extensions/src/main/java/org/apache/nifi/redis/service/RedisDistributedMapCacheClientService.java b/nifi-nar-bundles/nifi-redis-bundle/nifi-redis-extensions/src/main/java/org/apache/nifi/redis/service/RedisDistributedMapCacheClientService.java
index 45ceef2..7fd6c9b 100644
--- a/nifi-nar-bundles/nifi-redis-bundle/nifi-redis-extensions/src/main/java/org/apache/nifi/redis/service/RedisDistributedMapCacheClientService.java
+++ b/nifi-nar-bundles/nifi-redis-bundle/nifi-redis-extensions/src/main/java/org/apache/nifi/redis/service/RedisDistributedMapCacheClientService.java
@@ -161,8 +161,9 @@
                 final List<Object> results = redisConnection.exec();
 
                 // if the results list was empty, then the transaction failed (i.e. key was modified after we started watching), so keep looping to retry
+                // if the results list was null, then the transaction failed
                 // if the results list has results, then the transaction succeeded and it should have the result of the setNX operation
-                if (results.size() > 0) {
+                if (results != null && results.size() > 0) {
                     final Object firstResult = results.get(0);
                     if (firstResult instanceof Boolean) {
                         final Boolean absent = (Boolean) firstResult;
@@ -337,7 +338,7 @@
             final List<Object> results = redisConnection.exec();
 
             // if we have a result then the replace succeeded
-            if (results.size() > 0) {
+            if (results != null && results.size() > 0) {
                 replaced = true;
             }