diff --git a/NEWS b/NEWS
index ff16465c2..9f00893ae 100644
--- a/NEWS
+++ b/NEWS
@@ -5,6 +5,8 @@ Any uppercase BUG_* names are modernish shell bug IDs.
 
 2021-11-29:
 
+- Fixed a memory fault that prevented ksh from functioning on ARM-based Macs.
+
 - A bug that caused the time keyword to override the errexit shell option has
   been fixed.
 
diff --git a/src/cmd/ksh93/README b/src/cmd/ksh93/README
index d7229946d..9c5abd031 100644
--- a/src/cmd/ksh93/README
+++ b/src/cmd/ksh93/README
@@ -262,6 +262,7 @@ failures (crashes, and/or important functionality does not work).
 *	illumos: OmniOS 2020-08-19 (gcc) on x86_64
 	macOS 10.13.6 (High Sierra) on x86_64
 	macOS 10.14.6 (Mojave) on x86_64
+*	macOS 12.0.1 (Monterey) on ARM64
 *	NetBSD 8.1 on x86_64
 *	NetBSD 9.2 on x86_64
 *	OpenBSD 6.8 on x86_64
diff --git a/src/lib/libast/comp/omitted.c b/src/lib/libast/comp/omitted.c
index 247aa52bf..4668b7ac7 100644
--- a/src/lib/libast/comp/omitted.c
+++ b/src/lib/libast/comp/omitted.c
@@ -1092,9 +1092,7 @@ utime(const char* path, const struct utimbuf* ut)
  * own bsd-like macros
  */
 
-#if !_lib_bzero || defined(bzero)
-
-#undef	bzero
+#if !_lib_bzero
 
 void
 bzero(void* b, size_t n)