diff --git a/scripts/makefile.darwin b/scripts/makefile.darwin
index d6647bc5d..337a8151e 100644
--- a/scripts/makefile.darwin
+++ b/scripts/makefile.darwin
@@ -37,7 +37,7 @@ MKDIR_P=mkdir -p
 LN_SF=ln -sf
 RANLIB=ranlib
 RM_F=/bin/rm -f
-ARCH=-arch i386
+ARCH="-arch i386 -arch x86_64"
 
 # CFLAGS=-I$(ZLIBINC) -W -Wall -O3 -funroll-loops
 CFLAGS=-I$(ZLIBINC) -W -Wall -O -funroll-loops $(ARCH)