diff --git a/mozilla/config/build_header.pl b/mozilla/config/build_header.pl
new file mode 100644
index 00000000000..30ebc2c3a0a
--- /dev/null
+++ b/mozilla/config/build_header.pl
@@ -0,0 +1,12 @@
+open INFILE, "<$ARGV[1]";
+$build = <INFILE>;
+close INFILE;
+chop $build;
+open OUTFILE, ">$ARGV[0]" || die;
+
+print OUTFILE "/* THIS IS A GENERATED FILE!\n*\n";
+print OUTFILE "* See mozilla/config/build_header.pl */\n*\n*/";
+print OUTFILE "\n\#define NS_BUILD_ID " . $build . "\n";
+
+close OUTFILE;
+