diff -r 3b2dea75431e -r ae065c367d93 src/cpu/x86/vm/assembler_x86.cpp
--- a/src/cpu/x86/vm/assembler_x86.cpp	Sat Oct 30 13:08:23 2010 -0700
+++ b/src/cpu/x86/vm/assembler_x86.cpp	Tue Nov 02 09:00:37 2010 -0700
@@ -1288,7 +1288,7 @@
   if (is8bit(value)) {
     emit_byte(0x6B);
     emit_byte(0xC0 | encode);
-    emit_byte(value);
+    emit_byte(value & 0xFF);
   } else {
     emit_byte(0x69);
     emit_byte(0xC0 | encode);
@@ -3903,7 +3903,7 @@
   if (is8bit(value)) {
     emit_byte(0x6B);
     emit_byte(0xC0 | encode);
-    emit_byte(value);
+    emit_byte(value & 0xFF);
   } else {
     emit_byte(0x69);
     emit_byte(0xC0 | encode);