Plack::Test::Suite # add test case

diff --git a/lib/Plack/Test/Suite.pm b/lib/Plack/Test/Suite.pm
index 7189243..c575ce5 100644
--- a/lib/Plack/Test/Suite.pm
+++ b/lib/Plack/Test/Suite.pm
@@ -614,6 +614,24 @@ our @TEST = (
             return [ 200, [ "Content-Type", "text/plain" ], [ "OK" ] ];
         },
     ],
+    [
+        'Content-Length => 0 is not set Transfer-Encoding # regression test',
+        sub {
+            my $cb = shift;
+            my $res = $cb->(GET "http://127.0.0.1/");
+            is $res->code, 200;
+            is $res->header('Client-Transfer-Encoding'), undef;
+            is $res->content, '';
+        },
+        sub {
+            my $env = shift;
+            return [
+                200,
+                [ 'Content-Length' => '0' ],
+                ['' ],
+            ];
+        },
+    ],
 );

 sub runtests {

Starman::Server # patch

diff --git a/lib/Starman/Server.pm b/lib/Starman/Server.pm
index bf11ed4..1ae048e 100644
--- a/lib/Starman/Server.pm
+++ b/lib/Starman/Server.pm
@@ -408,7 +408,7 @@ sub _finalize_response {
     }

     if ( $protocol eq 'HTTP/1.1' ) {
-        if ( !$headers{'content-length'} ) {
+        if ( !exists $headers{'content-length'} ) {
             if ( $status !~ /^1\d\d|[23]04$/ ) {
                 DEBUG && warn "[$$] Using chunked transfer-encoding to send unknown length body\n";
                 push @headers, 'Transfer-Encoding: chunked';
@@ -422,7 +422,7 @@ sub _finalize_response {
             }
         }
     } else {
-        if ( !$headers{'content-length'} ) {
+        if ( !exists $headers{'content-length'} ) {
             DEBUG && warn "[$$] Disabling keep-alive after sending unknown length body on $protocol\n";
             $self->{client}->{keepalive} = 0;
         }