diff --git a/modules/src/main/java/org/archive/modules/credential/Credential.java b/modules/src/main/java/org/archive/modules/credential/Credential.java
index ca232942..2f23d630 100644
--- a/modules/src/main/java/org/archive/modules/credential/Credential.java
+++ b/modules/src/main/java/org/archive/modules/credential/Credential.java
@@ -46,7 +46,7 @@ import org.archive.modules.net.ServerCache;
  */
 public abstract class Credential implements Serializable {
 
-    private static final long serialVersionUID = 1L;
+    private static final long serialVersionUID = 2L;
 
     private static final Logger logger =
         Logger.getLogger(Credential.class.getName());
diff --git a/modules/src/main/java/org/archive/modules/credential/HtmlFormCredential.java b/modules/src/main/java/org/archive/modules/credential/HtmlFormCredential.java
index f58099ad..2163b073 100644
--- a/modules/src/main/java/org/archive/modules/credential/HtmlFormCredential.java
+++ b/modules/src/main/java/org/archive/modules/credential/HtmlFormCredential.java
@@ -43,7 +43,7 @@ import org.archive.net.UURIFactory;
  * @version $Revision$, $Date$
  */
 public class HtmlFormCredential extends Credential {
-    private static final long serialVersionUID = -3L;
+    private static final long serialVersionUID = -4L;
 
     private static final Logger logger =
         Logger.getLogger(HtmlFormCredential.class.getName());
diff --git a/modules/src/main/java/org/archive/modules/credential/HttpAuthenticationCredential.java b/modules/src/main/java/org/archive/modules/credential/HttpAuthenticationCredential.java
index bb161795..75aa8932 100644
--- a/modules/src/main/java/org/archive/modules/credential/HttpAuthenticationCredential.java
+++ b/modules/src/main/java/org/archive/modules/credential/HttpAuthenticationCredential.java
@@ -46,7 +46,7 @@ import org.archive.modules.CrawlURI;
  * @version $Revision$, $Date$
  */
 public class HttpAuthenticationCredential extends Credential {
-    private static final long serialVersionUID = 3L;
+    private static final long serialVersionUID = 4L;
 
     private static Logger logger =
         Logger.getLogger(HttpAuthenticationCredential.class.getName());