diff --git a/hikaricp-java6/src/main/java/com/zaxxer/hikari/proxy/ConnectionProxy.java b/hikaricp-java6/src/main/java/com/zaxxer/hikari/proxy/ConnectionProxy.java
index 5c47edc2..f801a182 100644
--- a/hikaricp-java6/src/main/java/com/zaxxer/hikari/proxy/ConnectionProxy.java
+++ b/hikaricp-java6/src/main/java/com/zaxxer/hikari/proxy/ConnectionProxy.java
@@ -56,9 +56,9 @@ public abstract class ConnectionProxy implements IHikariConnectionProxy
    private boolean isAnythingDirty;
    private boolean isAutoCommitDirty;
    private boolean isCatalogDirty;
-   private boolean isClosed;
    private boolean isReadOnlyDirty;
    private boolean isTransactionIsolationDirty;
+   private volatile boolean isClosed;
 
    // static initializer
    static {
diff --git a/hikaricp/src/main/java/com/zaxxer/hikari/proxy/ConnectionProxy.java b/hikaricp/src/main/java/com/zaxxer/hikari/proxy/ConnectionProxy.java
index 5c47edc2..f801a182 100644
--- a/hikaricp/src/main/java/com/zaxxer/hikari/proxy/ConnectionProxy.java
+++ b/hikaricp/src/main/java/com/zaxxer/hikari/proxy/ConnectionProxy.java
@@ -56,9 +56,9 @@ public abstract class ConnectionProxy implements IHikariConnectionProxy
    private boolean isAnythingDirty;
    private boolean isAutoCommitDirty;
    private boolean isCatalogDirty;
-   private boolean isClosed;
    private boolean isReadOnlyDirty;
    private boolean isTransactionIsolationDirty;
+   private volatile boolean isClosed;
 
    // static initializer
    static {