diff --git a/smack-core/src/main/java/org/jivesoftware/smack/util/LazyStringBuilder.java b/smack-core/src/main/java/org/jivesoftware/smack/util/LazyStringBuilder.java
index 6eb214b72a..6e0ded1348 100644
--- a/smack-core/src/main/java/org/jivesoftware/smack/util/LazyStringBuilder.java
+++ b/smack-core/src/main/java/org/jivesoftware/smack/util/LazyStringBuilder.java
@@ -24,7 +24,7 @@ public class LazyStringBuilder implements Appendable, CharSequence {
 
     private final List<CharSequence> list;
 
-    private String cache;
+    private transient String cache;
     private int cachedLength = -1;
 
     private void invalidateCache() {