diff --git a/src/compiler/codegen/x86/Assemble.cc b/src/compiler/codegen/x86/Assemble.cc
index 3a86bed..b9605cc 100644
--- a/src/compiler/codegen/x86/Assemble.cc
+++ b/src/compiler/codegen/x86/Assemble.cc
@@ -269,7 +269,7 @@
   EXT_0F_ENCODING_MAP(Divsd,     0xF2, 0x5E),
   EXT_0F_ENCODING_MAP(Divss,     0xF3, 0x5E),
 
-  { kX86PsllqRI, kRegImm, IS_BINARY_OP, { 0, 0, 0x0F, 0x73, 0, 6, 0, 1 }, "PsllqRI", "!0r, !1d" },
+  { kX86PsllqRI, kRegImm, IS_BINARY_OP, { 0x66, 0, 0x0F, 0x73, 0, 6, 0, 1 }, "PsllqRI", "!0r, !1d" },
 
   EXT_0F_ENCODING_MAP(Movdxr,    0x66, 0x6E),
   EXT_0F_ENCODING_MAP(Movdrx,    0x66, 0x7E),