lock.diff

diff --git a/lib/Mojo/Loader.pm b/lib/Mojo/Loader.pm
index f1038fa..c9eb7de 100644
--- a/lib/Mojo/Loader.pm
+++ b/lib/Mojo/Loader.pm
@@ -1,13 +1,17 @@
 package Mojo::Loader;
 use Mojo::Base -base;
 
+use Fcntl ':flock';
 use File::Basename 'fileparse';
 use File::Spec::Functions qw(catdir catfile splitdir);
+use File::Temp 'tempfile';
 use Mojo::Exception;
 use Mojo::Util qw(b64_decode class_to_path);
 
 my (%BIN, %CACHE);
 
+my $LOCK = tempfile;
+
 sub data { $_[1] ? $_[2] ? _all($_[1])->{$_[2]} : _all($_[1]) : undef }
 
 sub is_binary { keys %{_all($_[1])} ? !!$BIN{$_[1]}{$_[2]} : undef }
@@ -52,8 +56,10 @@ sub _all {
   return $CACHE{$class} if $CACHE{$class};
   my $handle = do { no strict 'refs'; \*{"${class}::DATA"} };
   return {} unless fileno $handle;
+  flock $LOCK, LOCK_EX;
   seek $handle, 0, 0;
   my $data = join '', <$handle>;
+  flock $LOCK, LOCK_UN;
 
   # Ignore everything before __DATA__ (Windows will seek to start of file)
   $data =~ s/^.*\n__DATA__\r?\n/\n/s;