diff --git a/src/main/java/com/zaxxer/hikari/pool/PoolBase.java b/src/main/java/com/zaxxer/hikari/pool/PoolBase.java
index 90e3252bd..4ac82c750 100644
--- a/src/main/java/com/zaxxer/hikari/pool/PoolBase.java
+++ b/src/main/java/com/zaxxer/hikari/pool/PoolBase.java
@@ -72,7 +72,7 @@ abstract class PoolBase
    private static final int MINIMUM_LOGIN_TIMEOUT = Integer.getInteger("com.zaxxer.hikari.minimumLoginTimeoutSecs", 1);
 
    private int networkTimeout;
-   private int isNetworkTimeoutSupported;
+   private volatile int isNetworkTimeoutSupported;
    private int isQueryTimeoutSupported;
    private int defaultTransactionIsolation;
    private int transactionIsolation;
@@ -243,6 +243,7 @@ void resetConnectionState(final Connection connection, final ProxyConnection pro
 
    void shutdownNetworkTimeoutExecutor()
    {
+      isNetworkTimeoutSupported = UNINITIALIZED;
       if (netTimeoutExecutor instanceof ThreadPoolExecutor) {
          ((ThreadPoolExecutor) netTimeoutExecutor).shutdownNow();
       }