diff --git a/tools/tests/x86_emulator/predicates.c b/tools/tests/x86_emulator/predicates.c
index afe2e297d9..f194c209ed 100644
--- a/tools/tests/x86_emulator/predicates.c
+++ b/tools/tests/x86_emulator/predicates.c
@@ -1945,7 +1945,7 @@ static const struct evex {
     { { 0x83 }, 2, T, R, pfx_66, W1, Ln }, /* vpmultishiftqb */
     { { 0x88 }, 2, T, R, pfx_66, Wn, Ln }, /* vpexpandp{s,d} */
     { { 0x89 }, 2, T, R, pfx_66, Wn, Ln }, /* vpexpand{d,q} */
-    { { 0x8a }, 2, T, W, pfx_66, Wn, Ln }, /* vpcompressp{s,d} */
+    { { 0x8a }, 2, T, W, pfx_66, Wn, Ln }, /* vcompressp{s,d} */
     { { 0x8b }, 2, T, W, pfx_66, Wn, Ln }, /* vpcompress{d,q} */
     { { 0x8d }, 2, F, R, pfx_66, Wn, Ln }, /* vperm{b,w} */
     { { 0x8f }, 2, F, R, pfx_66, W0, Ln }, /* vpshufbitqmb */
diff --git a/xen/arch/x86/x86_emulate/x86_emulate.c b/xen/arch/x86/x86_emulate/x86_emulate.c
index 2aedd4d155..c9cf30b443 100644
--- a/xen/arch/x86/x86_emulate/x86_emulate.c
+++ b/xen/arch/x86/x86_emulate/x86_emulate.c
@@ -6174,9 +6174,11 @@ x86_emulate(
             ASSERT(op_bytes == n * elem_bytes);
             op_mask &= ~0ULL >> (64 - n);
             n = hweight64(op_mask);
-            op_bytes = n * elem_bytes;
             if ( n )
+            {
+                op_bytes = n * elem_bytes;
                 op_mask = ~0ULL >> (64 - n);
+            }
         }
         goto simd_zmm;