diff --git a/common.mk b/common.mk
index 21ccd20..93ceef0 100644
--- a/common.mk
+++ b/common.mk
@@ -3,6 +3,9 @@ UNAME_S=$(shell uname -s)
 ifeq ($(UNAME_S),Linux)
   OS=Linux
 endif
+ifeq ($(UNAME_S),Darwin)
+  ARCH=x86_64
+endif
 ARCH?=$(shell arch)
 ifeq ($(ARCH),x86_64)
   CPU=x86-64
@@ -10,7 +13,7 @@ ifeq ($(ARCH),x86_64)
   BIT=64
   BIT_OPT=-m64
   #LOW_ASM_SRC=src/asm/low_x86-64.asm
-  ASM=nasm -felf64
+  #ASM=nasm -felf64
 endif
 ifeq ($(ARCH),x86)
   CPU=x86
diff --git a/readme.md b/readme.md
index 7e49b18..73f8e55 100644
--- a/readme.md
+++ b/readme.md
@@ -68,6 +68,14 @@ open mcl.sln and build or if you have msbuild.exe
 ```
 msbuild /p:Configuration=Release
 ```
+
+## Build for MacOS
+Install openssl and [llvm](http://releases.llvm.org/download.html) and add `<installed llvm dir>/bin/` to the path.
+```
+make UPDATE_ASM=1
+make -j test CFLAGS_USER=-I/usr/local/opt/openssl/include LDFLAGS_USER=-L/usr/local/opt/openssl/lib
+```
+
 ## Benchmark
 
 A benchmark of a BN curve over the 254-bit prime p = 36z^4 + 36z^3 + 24z^2 + 6z + 1 where z = -(2^62 + 2^55 + 1).