--- old/src/java.base/share/classes/java/lang/StringBuffer.java	2016-12-09 08:31:42.489367329 +0100
+++ new/src/java.base/share/classes/java/lang/StringBuffer.java	2016-12-09 08:31:42.347368396 +0100
@@ -427,6 +427,13 @@
         return this;
     }
 
+    @Override
+    public synchronized StringBuffer appendN(char c, int n) {
+        toStringCache = null;
+        super.appendN(c, n);
+        return this;
+    }
+
     /**
      * @throws StringIndexOutOfBoundsException {@inheritDoc}
      * @since      1.2