diff --git a/BUILDING.md b/BUILDING.md
index d5d3fa0..eab61e2 100644
--- a/BUILDING.md
+++ b/BUILDING.md
@@ -32,9 +32,8 @@
   * [Go](https://golang.org/dl/) is required. If not found by CMake, the go
     executable may be configured explicitly by setting `GO_EXECUTABLE`.
 
-  * To build the x86 and x86\_64 assembly, your assembler must support AVX2,
-    MOVBE, and ADX. If using GNU binutils, you must have 2.23 or later. If using
-    Yasm, you must have 1.3.0 or later.
+  * To build the x86 and x86\_64 assembly, your assembler must support AVX2
+    instructions and MOVBE. If using GNU binutils, you must have 2.22 or later
 
 ## Building
 
diff --git a/crypto/fipsmodule/bn/asm/rsaz-avx2.pl b/crypto/fipsmodule/bn/asm/rsaz-avx2.pl
index 437c0f7..0bb50cd 100755
--- a/crypto/fipsmodule/bn/asm/rsaz-avx2.pl
+++ b/crypto/fipsmodule/bn/asm/rsaz-avx2.pl
@@ -82,8 +82,10 @@
 # In upstream, this is controlled by shelling out to the compiler to check
 # versions, but BoringSSL is intended to be used with pre-generated perlasm
 # output, so this isn't useful anyway.
+#
+# TODO(davidben): Set $addx to one once build problems are resolved.
 $avx = 2;
-$addx = 1;
+$addx = 0;
 
 open OUT,"| \"$^X\" \"$xlate\" $flavour \"$output\"";
 *STDOUT = *OUT;
diff --git a/crypto/fipsmodule/bn/asm/x86_64-mont.pl b/crypto/fipsmodule/bn/asm/x86_64-mont.pl
index c27f65d..b57537e 100755
--- a/crypto/fipsmodule/bn/asm/x86_64-mont.pl
+++ b/crypto/fipsmodule/bn/asm/x86_64-mont.pl
@@ -56,7 +56,9 @@
 # In upstream, this is controlled by shelling out to the compiler to check
 # versions, but BoringSSL is intended to be used with pre-generated perlasm
 # output, so this isn't useful anyway.
-$addx = 1;
+#
+# TODO(davidben): Set $addx to one once build problems are resolved.
+$addx = 0;
 
 # int bn_mul_mont(
 $rp="%rdi";	# BN_ULONG *rp,
diff --git a/crypto/fipsmodule/bn/asm/x86_64-mont5.pl b/crypto/fipsmodule/bn/asm/x86_64-mont5.pl
index 73abb71..dfb8b37 100755
--- a/crypto/fipsmodule/bn/asm/x86_64-mont5.pl
+++ b/crypto/fipsmodule/bn/asm/x86_64-mont5.pl
@@ -41,7 +41,9 @@
 # In upstream, this is controlled by shelling out to the compiler to check
 # versions, but BoringSSL is intended to be used with pre-generated perlasm
 # output, so this isn't useful anyway.
-$addx = 1;
+#
+# TODO(davidben): Set $addx to one once build problems are resolved.
+$addx = 0;
 
 # int bn_mul_mont_gather5(
 $rp="%rdi";	# BN_ULONG *rp,
diff --git a/crypto/fipsmodule/ec/asm/p256-x86_64-asm.pl b/crypto/fipsmodule/ec/asm/p256-x86_64-asm.pl
index ff5756f..7ae2d5e 100755
--- a/crypto/fipsmodule/ec/asm/p256-x86_64-asm.pl
+++ b/crypto/fipsmodule/ec/asm/p256-x86_64-asm.pl
@@ -54,8 +54,9 @@
 open OUT,"| \"$^X\" \"$xlate\" $flavour \"$output\"";
 *STDOUT=*OUT;
 
+# TODO(davidben): Set $addx to one once build problems are resolved.
 $avx = 2;
-$addx = 1;
+$addx = 0;
 
 $code.=<<___;
 .text