diff --git a/spring-cloud-loadbalancer/src/main/java/org/springframework/cloud/loadbalancer/core/ZonePreferenceServiceInstanceListSupplier.java b/spring-cloud-loadbalancer/src/main/java/org/springframework/cloud/loadbalancer/core/ZonePreferenceServiceInstanceListSupplier.java
index dafbbad7..8d11ca13 100644
--- a/spring-cloud-loadbalancer/src/main/java/org/springframework/cloud/loadbalancer/core/ZonePreferenceServiceInstanceListSupplier.java
+++ b/spring-cloud-loadbalancer/src/main/java/org/springframework/cloud/loadbalancer/core/ZonePreferenceServiceInstanceListSupplier.java
@@ -39,7 +39,7 @@ import org.springframework.cloud.loadbalancer.config.LoadBalancerZoneConfig;
  */
 public class ZonePreferenceServiceInstanceListSupplier extends DelegatingServiceInstanceListSupplier {
 
-	private final String ZONE = "zone";
+	private static final String ZONE = "zone";
 
 	private final LoadBalancerZoneConfig zoneConfig;