diff --git a/src/main/java/com/zaxxer/hikari/proxy/ConnectionProxy.java b/src/main/java/com/zaxxer/hikari/proxy/ConnectionProxy.java
index a6e7b7e0..c4fe4a14 100644
--- a/src/main/java/com/zaxxer/hikari/proxy/ConnectionProxy.java
+++ b/src/main/java/com/zaxxer/hikari/proxy/ConnectionProxy.java
@@ -71,6 +71,7 @@ public abstract class ConnectionProxy implements IHikariConnectionProxy
 
         creationTime = lastAccess = System.currentTimeMillis();
         openStatements = new FastStatementList();
+        isTransactionIsolationDirty = true;
     }
     
     public final void unregisterStatement(Object statement)