diff --git a/core/src/main/java/org/acegisecurity/acls/MutableAcl.java b/core/src/main/java/org/acegisecurity/acls/MutableAcl.java
index 394de6230d..683230fd2f 100644
--- a/core/src/main/java/org/acegisecurity/acls/MutableAcl.java
+++ b/core/src/main/java/org/acegisecurity/acls/MutableAcl.java
@@ -68,7 +68,7 @@ public interface MutableAcl extends Acl {
      *
      * @param newParent the new parent
      */
-    void setParent(MutableAcl newParent);
+    void setParent(Acl newParent);
 
     void updateAce(Serializable aceId, Permission permission)
         throws NotFoundException;
diff --git a/core/src/main/java/org/acegisecurity/acls/domain/AclImpl.java b/core/src/main/java/org/acegisecurity/acls/domain/AclImpl.java
index ac290fd194..fd454c3c68 100644
--- a/core/src/main/java/org/acegisecurity/acls/domain/AclImpl.java
+++ b/core/src/main/java/org/acegisecurity/acls/domain/AclImpl.java
@@ -335,7 +335,7 @@ public class AclImpl implements Acl, MutableAcl, AuditableAcl, OwnershipAcl {
         this.owner = newOwner;
     }
 
-    public void setParent(MutableAcl newParent) {
+    public void setParent(Acl newParent) {
         aclAuthorizationStrategy.securityCheck(this, AclAuthorizationStrategy.CHANGE_GENERAL);
         Assert.notNull(newParent, "New Parent required");
         Assert.isTrue(!newParent.equals(this), "Cannot be the parent of yourself");