diff --git a/libs/libc/machine/xtensa/arch_memmove.S b/libs/libc/machine/xtensa/arch_memmove.S
index 7ce56c47b70..f3a1d89b68a 100644
--- a/libs/libc/machine/xtensa/arch_memmove.S
+++ b/libs/libc/machine/xtensa/arch_memmove.S
@@ -396,6 +396,7 @@ memmove:
   _beqz a4, .Lbackdone  # avoid loading anything for zero-length copies
   # copy 16 bytes per iteration for word-aligned dst and unaligned src
   ssa8  a3    # set shift amount from byte offset
+#undef SIM_CHECKS_ALIGNMENT
 #define SIM_CHECKS_ALIGNMENT  1 /* set to 1 when running on ISS with
            * the lint or ferret client, or 0
            * to save a few cycles */