diff -up ./core/java12/com/vladium/emma/instr/InstrVisitor.java.64bitfix ./core/java12/com/vladium/emma/instr/InstrVisitor.java
--- ./core/java12/com/vladium/emma/instr/InstrVisitor.java.64bitfix	2004-07-16 18:32:28.000000000 -0400
+++ ./core/java12/com/vladium/emma/instr/InstrVisitor.java	2008-12-10 09:37:04.000000000 -0500
@@ -1435,6 +1435,7 @@ final class InstrVisitor extends Abstrac
          */
         void emit (final EmitCtx ctx, final byte [] code) // TODO: move 'code' into 'ctx'
         {
+        	synchronized(Block.class) {
             final ByteArrayOStream out = ctx.m_out;
             final int first = m_first;
             
@@ -1450,6 +1451,7 @@ final class InstrVisitor extends Abstrac
             
             if (m_branch != null)
                 m_branch.emit (ctx);
+		}
         }
         
         public CodeSegment m_insertion;
@@ -2206,4 +2208,4 @@ final class InstrVisitor extends Abstrac
     private static final byte [] EMPTY_BYTE_ARRAY = new byte [0];
 
 } // end of class
-// ----------------------------------------------------------------------------
\ No newline at end of file
+// ----------------------------------------------------------------------------