diff -r 9d60798b21af -r ff1c86e85d02 src/jdk.jshell/share/classes/jdk/internal/jshell/tool/StopDetectingInputStream.java
--- a/src/jdk.jshell/share/classes/jdk/internal/jshell/tool/StopDetectingInputStream.java	Wed Dec 12 23:08:01 2018 -0800
+++ b/src/jdk.jshell/share/classes/jdk/internal/jshell/tool/StopDetectingInputStream.java	Thu Dec 13 08:26:07 2018 +0100
@@ -113,7 +113,7 @@
     }
 
     public synchronized void write(int b) {
-        if (state != State.BUFFER) {
+        if (state == State.READ) {
             state = State.WAIT;
         }
         int newEnd = (end + 1) % buffer.length;