diff --git a/gas/ChangeLog b/gas/ChangeLog
index 2c962951be4..f0b70be4c43 100644
--- a/gas/ChangeLog
+++ b/gas/ChangeLog
@@ -1,3 +1,8 @@
+2010-09-09  H.J. Lu  <hongjiu.lu@intel.com>
+
+	* config/tc-i386.c (build_vex_prefix): Check VEXW1 for 2-byte
+	VEX prefix.
+
 2010-09-09  Joseph Myers  <joseph@codesourcery.com>
 
 	* doc/c-tic6x.texi (.c6xabi_attribute): Document directive.
diff --git a/gas/config/tc-i386.c b/gas/config/tc-i386.c
index 9488ac933e1..ee3470e48a2 100644
--- a/gas/config/tc-i386.c
+++ b/gas/config/tc-i386.c
@@ -2803,6 +2803,7 @@ build_vex_prefix (const insn_template *t)
 
   /* Use 2-byte VEX prefix if possible.  */
   if (i.tm.opcode_modifier.vexopcode == VEX0F
+      && i.tm.opcode_modifier.vexw != VEXW1
       && (i.rex & (REX_W | REX_X | REX_B)) == 0)
     {
       /* 2-byte VEX prefix.  */