diff --git a/resolver/src/main/java/org/apache/james/jspf/executor/FutureSPFResult.java b/resolver/src/main/java/org/apache/james/jspf/executor/FutureSPFResult.java
index 2eb336e..687d6be 100644
--- a/resolver/src/main/java/org/apache/james/jspf/executor/FutureSPFResult.java
+++ b/resolver/src/main/java/org/apache/james/jspf/executor/FutureSPFResult.java
@@ -105,7 +105,7 @@
      * 
      * @return true or false
      */
-    public boolean isReady() {
+    public synchronized boolean isReady() {
         return isReady;
     }
 }