diff -r 2d537f8cd604 -r 04e312a7887e vm/src/main/java/org/apidesign/vm4brwsr/ByteCodeToJavaScript.java
--- a/vm/src/main/java/org/apidesign/vm4brwsr/ByteCodeToJavaScript.java	Fri Feb 01 06:09:18 2013 +0100
+++ b/vm/src/main/java/org/apidesign/vm4brwsr/ByteCodeToJavaScript.java	Fri Feb 01 09:00:30 2013 +0100
@@ -600,7 +600,7 @@
                     emit(out, "@1 = -@1;", smapper.getI(0));
                     break;
                 case opc_lneg:
-                    emit(out, "@1 = -@1;", smapper.getL(0));
+                    emit(out, "@1 = @1.neg64();", smapper.getL(0));
                     break;
                 case opc_fneg:
                     emit(out, "@1 = -@1;", smapper.getF(0));