diff --git a/langtools/src/jdk.jshell/share/classes/jdk/jshell/Diag.java b/langtools/src/jdk.jshell/share/classes/jdk/jshell/Diag.java
index 396396dec2a..c24578b3369 100644
--- a/langtools/src/jdk.jshell/share/classes/jdk/jshell/Diag.java
+++ b/langtools/src/jdk.jshell/share/classes/jdk/jshell/Diag.java
@@ -35,13 +35,19 @@ import javax.tools.Diagnostic;
 public abstract class Diag {
     // Simplified view on compiler Diagnostic.
 
+    /**
+     * In-package creation only.
+     */
+    Diag() {
+    }
+
     /**
      * Used to signal that no position is available.
      */
     public final static long NOPOS = Diagnostic.NOPOS;
 
     /**
-     * Is this diagnostic and error (as opposed to a warning or note)
+     * Is this diagnostic an error (as opposed to a warning or note)
      * @return true if this diagnostic is an error
      */
     public abstract boolean isError();