diff --git a/object-pool/src/main/java/com/iluwatar/object/pool/ObjectPool.java b/object-pool/src/main/java/com/iluwatar/object/pool/ObjectPool.java
index df6e887b8..e76d00352 100644
--- a/object-pool/src/main/java/com/iluwatar/object/pool/ObjectPool.java
+++ b/object-pool/src/main/java/com/iluwatar/object/pool/ObjectPool.java
@@ -55,7 +55,7 @@ public abstract class ObjectPool<T> {
   }
 
   @Override
-  public String toString() {
+  public synchronized String toString() {
     return String.format("Pool available=%d inUse=%d", available.size(), inUse.size());
   }
 }