diff -r aeadaf905d78 -r d04960f05593 src/share/classes/com/sun/tools/javac/jvm/ClassWriter.java
--- a/src/share/classes/com/sun/tools/javac/jvm/ClassWriter.java	Wed Feb 13 10:33:13 2013 +0100
+++ b/src/share/classes/com/sun/tools/javac/jvm/ClassWriter.java	Wed Feb 13 17:04:21 2013 +0000
@@ -728,14 +728,24 @@
      * Write method parameter names attribute.
      */
     int writeMethodParametersAttr(MethodSymbol m) {
-        if (m.params != null && 0 != m.params.length()) {
-            int attrIndex = writeAttr(names.MethodParameters);
-            databuf.appendByte(m.params.length());
+        MethodType ty = m.externalType(types).asMethodType();
+        final int allparams = ty.argtypes.size();
+        if (m.params != null && allparams != 0) {
+            final int attrIndex = writeAttr(names.MethodParameters);
+            databuf.appendByte(allparams);
+            // Write extra parameters first
+            for (VarSymbol s : m.extraParams) {
+                final int flags =
+                    ((int) s.flags() & (FINAL | SYNTHETIC | MANDATED)) |
+                    ((int) m.flags() & SYNTHETIC);
+                databuf.appendChar(pool.put(s.name));
+                databuf.appendInt(flags);
+            }
+            // Now write the real parameters
             for (VarSymbol s : m.params) {
-                // TODO: expand to cover synthesized, once we figure out
-                // how to represent that.
-                final int flags = (int) s.flags() & (FINAL | SYNTHETIC);
-                // output parameter info
+                final int flags =
+                    ((int) s.flags() & (FINAL | SYNTHETIC | MANDATED)) |
+                    ((int) m.flags() & SYNTHETIC);
                 databuf.appendChar(pool.put(s.name));
                 databuf.appendInt(flags);
             }