diff --git a/libc/arch-x86_64/string/ssse3-strcmp-slm.S b/libc/arch-x86_64/string/ssse3-strcmp-slm.S
index 0dd8c27..e8acd5b 100644
--- a/libc/arch-x86_64/string/ssse3-strcmp-slm.S
+++ b/libc/arch-x86_64/string/ssse3-strcmp-slm.S
@@ -1897,8 +1897,8 @@
 
 	.p2align 4
 L(Byte0):
-	movzx	(%rsi), %ecx
-	movzx	(%rdi), %eax
+	movzbl	(%rsi), %ecx
+	movzbl	(%rdi), %eax
 
 	sub	%ecx, %eax
 	ret