diff --git a/core/src/main/java/hudson/security/csrf/DefaultCrumbIssuer.java b/core/src/main/java/hudson/security/csrf/DefaultCrumbIssuer.java
index a1b9a8e9ca71f42f9b48cc9a41b7ec5df6a21452..c69d9aac676b4bcbfa54f9826fee105dda9302fb 100644
--- a/core/src/main/java/hudson/security/csrf/DefaultCrumbIssuer.java
+++ b/core/src/main/java/hudson/security/csrf/DefaultCrumbIssuer.java
@@ -100,7 +100,7 @@ public class DefaultCrumbIssuer extends CrumbIssuer {
         return false;
     }
 
-    private final String PROXY_HEADER = "X-Forwarded-For";
+    private static final String PROXY_HEADER = "X-Forwarded-For";
 
     private String getClientIP(HttpServletRequest req) {
         String defaultAddress = req.getRemoteAddr();