diff -r 71b78a44c698 -r f8b3f053cfbb src/java.net.http/share/classes/jdk/internal/net/http/PlainTunnelingConnection.java
--- a/src/java.net.http/share/classes/jdk/internal/net/http/PlainTunnelingConnection.java	Mon Apr 16 13:57:06 2018 +0100
+++ b/src/java.net.http/share/classes/jdk/internal/net/http/PlainTunnelingConnection.java	Mon Apr 16 16:44:12 2018 +0100
@@ -61,10 +61,10 @@
 
     @Override
     public CompletableFuture<Void> connectAsync() {
-        debug.log(Level.DEBUG, "Connecting plain connection");
+        if (debug.on()) debug.log("Connecting plain connection");
         return delegate.connectAsync()
             .thenCompose((Void v) -> {
-                debug.log(Level.DEBUG, "sending HTTP/1.1 CONNECT");
+                if (debug.on()) debug.log("sending HTTP/1.1 CONNECT");
                 HttpClientImpl client = client();
                 assert client != null;
                 HttpRequestImpl req = new HttpRequestImpl("CONNECT", address, proxyHeaders);
@@ -76,7 +76,7 @@
                         .responseAsyncImpl(delegate)
                         .thenCompose((Response resp) -> {
                             CompletableFuture<Void> cf = new MinimalFuture<>();
-                            debug.log(Level.DEBUG, "got response: %d", resp.statusCode());
+                            if (debug.on()) debug.log("got response: %d", resp.statusCode());
                             if (resp.statusCode() == 407) {
                                 return connectExchange.ignoreBody().handle((r,t) -> {
                                     // close delegate after reading body: we won't