diff --git a/src/syscall/mkall.sh b/src/syscall/mkall.sh
index 739663ed9c4..85fab4ff3e3 100755
--- a/src/syscall/mkall.sh
+++ b/src/syscall/mkall.sh
@@ -179,7 +179,7 @@ linux_amd64)
 linux_arm)
 	mkerrors="$mkerrors"
 	mksyscall="./mksyscall.pl -l32 -arm"
-	mksysnum="curl -s 'http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/plain/arch/arm/include/uapi/asm/unistd.h' | ./mksysnum_linux.pl"
+	mksysnum="curl -s 'http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/plain/arch/arm/include/uapi/asm/unistd.h' | ./mksysnum_linux.pl -"
 	mktypes="GOARCH=$GOARCH go tool cgo -godefs"
 	;;
 linux_arm64)
diff --git a/src/syscall/mksysnum_linux.pl b/src/syscall/mksysnum_linux.pl
index 7a8add8bab2..b6fbcb599b1 100755
--- a/src/syscall/mksysnum_linux.pl
+++ b/src/syscall/mksysnum_linux.pl
@@ -28,7 +28,8 @@ sub fmt {
 }
 
 my $prev;
-while(<>){
+open(GCC, "gcc -E -dD $ARGV[0] |") || die "can't run gcc";
+while(<GCC>){
 	if(/^#define __NR_syscalls\s+/) {
 		# ignore redefinitions of __NR_syscalls
 	}