diff --git a/api/src/main/java/io/strimzi/api/kafka/model/bridge/KafkaBridgeConsumerEnablement.java b/api/src/main/java/io/strimzi/api/kafka/model/bridge/KafkaBridgeConsumerEnablement.java
index 8aa4b67a445..3cfd297d40c 100644
--- a/api/src/main/java/io/strimzi/api/kafka/model/bridge/KafkaBridgeConsumerEnablement.java
+++ b/api/src/main/java/io/strimzi/api/kafka/model/bridge/KafkaBridgeConsumerEnablement.java
@@ -31,6 +31,8 @@
 @ToString
 public class KafkaBridgeConsumerEnablement implements UnknownPropertyPreserving, Serializable {
 
+    private static final long serialVersionUID = 1L;
+
     private boolean enabled = true;
     private Map<String, Object> additionalProperties;
 
diff --git a/api/src/main/java/io/strimzi/api/kafka/model/bridge/KafkaBridgeProducerEnablement.java b/api/src/main/java/io/strimzi/api/kafka/model/bridge/KafkaBridgeProducerEnablement.java
index 1c669a04e89..a7e519c7935 100644
--- a/api/src/main/java/io/strimzi/api/kafka/model/bridge/KafkaBridgeProducerEnablement.java
+++ b/api/src/main/java/io/strimzi/api/kafka/model/bridge/KafkaBridgeProducerEnablement.java
@@ -31,6 +31,8 @@
 @ToString
 public class KafkaBridgeProducerEnablement implements UnknownPropertyPreserving, Serializable {
 
+    private static final long serialVersionUID = 1L;
+    
     private boolean enabled = true;
     private Map<String, Object> additionalProperties;
 
diff --git a/api/src/main/java/io/strimzi/api/kafka/model/common/ClientTls.java b/api/src/main/java/io/strimzi/api/kafka/model/common/ClientTls.java
index e93dea5a12e..68d0b1ab5f8 100644
--- a/api/src/main/java/io/strimzi/api/kafka/model/common/ClientTls.java
+++ b/api/src/main/java/io/strimzi/api/kafka/model/common/ClientTls.java
@@ -15,6 +15,7 @@
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.Objects;
 import java.util.stream.Collectors;
 
 import static java.util.Collections.emptyMap;
@@ -59,6 +60,7 @@ public void setAdditionalProperty(String name, Object value) {
     }
 
     public String toVarString() {
+        Objects.requireNonNull(this.trustedCertificates, "trustedCertificates cannot be null");
         return this.trustedCertificates.stream()
                 .map(certSecretSource -> certSecretSource.getSecretName() + "/" + certSecretSource.getCertificate())
                 .collect(Collectors.joining(";"));