--- a/src/java.net.http/share/classes/jdk/internal/net/http/websocket/WebSocketImpl.java	Wed Mar 21 19:18:59 2018 +0000
+++ b/src/java.net.http/share/classes/jdk/internal/net/http/websocket/WebSocketImpl.java	Thu Mar 22 09:48:27 2018 +0000
@@ -292,7 +292,7 @@
         if (!isLegalToSendFromClient(statusCode)) {
             result = failedFuture(new IllegalArgumentException("statusCode"));
         } else if (!isLegalReason(reason)) {
-            result = failedFuture(new IOException("reason"));
+            result = failedFuture(new IllegalArgumentException("reason"));
         } else if (!outputClosed.compareAndSet(false, true)){
             result = failedFuture(new IOException("Output closed"));
         } else {