diff --git a/libc/Android.bp b/libc/Android.bp
index 6042929..5334763 100644
--- a/libc/Android.bp
+++ b/libc/Android.bp
@@ -787,7 +787,7 @@
     arch: {
         arm: {
             cflags: [
-                "-DNO___MEMCPY_CHK",
+                "-DHAVE_ASSEMBLER___MEMCPY_CHK",
                 "-DRENAME___STRCAT_CHK",
                 "-DRENAME___STRCPY_CHK",
             ],
@@ -814,9 +814,10 @@
             ],
         },
         arm64: {
-            cflags: ["-DNO___MEMCPY_CHK"],
+            cflags: ["-DHAVE_ASSEMBLER___MEMCPY_CHK"],
             srcs: [
                 "arch-arm64/generic/bionic/__memcpy_chk.S",
+                "arch-arm64/generic/bionic/__memset_chk.S",
             ],
         },
     },
diff --git a/libc/arch-arm64/generic/bionic/__memset_chk.S b/libc/arch-arm64/generic/bionic/__memset_chk.S
new file mode 100644
index 0000000..e1e29d0
--- /dev/null
+++ b/libc/arch-arm64/generic/bionic/__memset_chk.S
@@ -0,0 +1,47 @@
+/*
+ * Copyright (C) 2017 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *  * Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <private/bionic_asm.h>
+
+ENTRY(__memset_chk)
+  cmp x2, x3
+  // Direct b.ls memcpy may not have enough range
+  b.hi .L_memset_chk_fail
+  b memset
+
+.L_memset_chk_fail:
+  // Preserve for accurate backtrace.
+  stp x29, x30, [sp, -16]!
+  .cfi_def_cfa_offset 16
+  .cfi_rel_offset x29, 0
+  .cfi_rel_offset x30, 8
+
+  bl __memset_chk_fail
+END(__memset_chk)
+
+NOTE_GNU_PROPERTY()
diff --git a/libc/arch-arm64/generic/bionic/memset.S b/libc/arch-arm64/generic/bionic/memset.S
index 19d3510..145ae63 100644
--- a/libc/arch-arm64/generic/bionic/memset.S
+++ b/libc/arch-arm64/generic/bionic/memset.S
@@ -85,19 +85,6 @@
 
 #define L(l) .L ## l
 
-ENTRY(__memset_chk)
-  cmp count, dst
-  bls memset
-
-  // Preserve for accurate backtrace.
-  stp x29, x30, [sp, -16]!
-  .cfi_def_cfa_offset 16
-  .cfi_rel_offset x29, 0
-  .cfi_rel_offset x30, 8
-
-  bl __memset_chk_fail
-END(__memset_chk)
-
 ENTRY(memset)
 
 	dup	v0.16B, valw
diff --git a/libc/bionic/fortify.cpp b/libc/bionic/fortify.cpp
index 88ae477..4317a56 100644
--- a/libc/bionic/fortify.cpp
+++ b/libc/bionic/fortify.cpp
@@ -489,14 +489,14 @@
   return strcpy(dst, src);
 }
 
-#if !defined(NO___MEMCPY_CHK)
+#if !defined(HAVE_ASSEMBLER___MEMCPY_CHK)
 // Runtime implementation of __memcpy_chk (used directly by compiler, not in headers).
 extern "C" void* __memcpy_chk(void* dst, const void* src, size_t count, size_t dst_len) {
   __check_count("memcpy", "count", count);
   __check_buffer_access("memcpy", "write into", count, dst_len);
   return memcpy(dst, src, count);
 }
-#endif // NO___MEMCPY_CHK
+#endif
 
 // Runtime implementation of __mempcpy_chk (used directly by compiler, not in headers).
 extern "C" void* __mempcpy_chk(void* dst, const void* src, size_t count, size_t dst_len) {