diff --git a/unix/.gitignore b/unix/.gitignore
new file mode 100644
index 00000000..e4827159
--- /dev/null
+++ b/unix/.gitignore
@@ -0,0 +1 @@
+_obj/
diff --git a/unix/mkall.sh b/unix/mkall.sh
index d41d6100..de95a4bb 100755
--- a/unix/mkall.sh
+++ b/unix/mkall.sh
@@ -116,12 +116,12 @@ _* | *_ | _)
 darwin_386)
 	mkerrors="$mkerrors -m32"
 	mksyscall="./mksyscall.pl -l32"
-	mksysnum="./mksysnum_darwin.pl /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.10.sdk/usr/include/sys/syscall.h"
+	mksysnum="./mksysnum_darwin.pl $(xcrun --show-sdk-path --sdk macosx)/usr/include/sys/syscall.h"
 	mktypes="GOARCH=$GOARCH go tool cgo -godefs"
 	;;
 darwin_amd64)
 	mkerrors="$mkerrors -m64"
-	mksysnum="./mksysnum_darwin.pl /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.10.sdk/usr/include/sys/syscall.h"
+	mksysnum="./mksysnum_darwin.pl $(xcrun --show-sdk-path --sdk macosx)/usr/include/sys/syscall.h"
 	mktypes="GOARCH=$GOARCH go tool cgo -godefs"
 	;;
 darwin_arm)
@@ -131,7 +131,7 @@ darwin_arm)
 	;;
 darwin_arm64)
 	mkerrors="$mkerrors -m64"
-	mksysnum="./mksysnum_darwin.pl /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS.sdk/usr/include/sys/syscall.h"
+	mksysnum="./mksysnum_darwin.pl $(xcrun --show-sdk-path --sdk iphoneos)/usr/include/sys/syscall.h"
 	mktypes="GOARCH=$GOARCH go tool cgo -godefs"
 	;;
 dragonfly_386)
diff --git a/unix/zsysnum_darwin_arm64.go b/unix/zsysnum_darwin_arm64.go
index 39537d21..26677ebb 100644
--- a/unix/zsysnum_darwin_arm64.go
+++ b/unix/zsysnum_darwin_arm64.go
@@ -1,4 +1,4 @@
-// mksysnum_darwin.pl /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS.sdk/usr/include/sys/syscall.h
+// mksysnum_darwin.pl /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS8.4.sdk/usr/include/sys/syscall.h
 // MACHINE GENERATED BY THE ABOVE COMMAND; DO NOT EDIT
 
 // +build arm64,darwin