diff --git a/Changelog b/Changelog
index ae9d1fd..1e676b5 100644
--- a/Changelog
+++ b/Changelog
@@ -1,3 +1,7 @@
+0.12
+	o revert commit 495fcbc, see #7: breaks backwards
+	  compatibility.
+
 0.11
 	o typos
 
diff --git a/Struct.pm b/Struct.pm
index 23938f1..951391f 100644
--- a/Struct.pm
+++ b/Struct.pm
@@ -21,7 +21,7 @@ use File::stat;
 use Data::Validate qw(:math is_printable);
 use Data::Validate::IP qw(is_ipv4 is_ipv6);
 
-our $VERSION = 0.11;
+our $VERSION = 0.12;
 
 use vars qw(@ISA);
 
@@ -195,14 +195,7 @@ sub _traverse {
   my ($self, $reference, $hash, @tree) = @_;
 
   foreach my $key (keys %{$reference}) {
-    my $reference_ref = ref $reference->{$key};
-    my $hash_ref = ref $hash->{$key};
-    if ($reference_ref =~ /^ARRAY|HASH$/ && $reference_ref ne $hash_ref)
-    {
-      my $err = sprintf("Different structure types %s vs %s", $reference_ref, $hash_ref);
-      push @{$self->{errors}}, sprintf(q{%s at '%s'}, $err, join(' => ', @tree));
-    }
-    elsif ($reference_ref eq 'ARRAY') {
+    if (ref($reference->{$key}) eq 'ARRAY') {
       # just use the 1st one, more elements in array are expected to be the same
       foreach my $item (@{$hash->{$key}}) {
         if (ref($item) eq q(HASH)) {
@@ -219,10 +212,10 @@ sub _traverse {
         }
       }
     }
-    elsif ($reference_ref eq 'HASH') {
+    elsif (ref($reference->{$key}) eq 'HASH') {
       $self->_traverse($reference->{$key}, $hash->{$key}, @tree, $key);
     }
-    elsif ($reference_ref eq '') {
+    elsif (ref($reference->{$key}) eq '') {
       $self->_debug("Checking $key at " . join(', ', @tree));
       if (my $err = $self->_check_type($key, $reference, $hash)) {
         push @{$self->{errors}}, sprintf(q{%s at '%s'}, $err, join(' => ', @tree));
diff --git a/t/run.t b/t/run.t
index d297654..697ee34 100644
--- a/t/run.t
+++ b/t/run.t
@@ -6,36 +6,36 @@ use Encode qw{ encode };
 require_ok( 'Data::Validate::Struct' );
 
 my $ref = {
-	   'b1' => {
+           'b1' => {
                     'b2' => {
-			     'b3' => {
-				      'item' => 'int'
-				     }
+                             'b3' => {
+                                      'item' => 'int'
+                                     }
                             }
-		   },
-	   'item' => [ 'number' ],
-	   'v1' => 'int',
-	   'v2' => 'number',
-	   'v3' => 'word',
-	   'v4' => 'line',
-	   'v5' => 'text',
-	   'v6' => 'hostname',
-	   'v8' => 'user',
-	   'v10' => 'port',
-	   'v11' => 'uri',
-	   'v12' => 'cidrv4',
-	   'v13' => 'ipv4',
-	   'v14' => 'path',
-	   'v15' => 'fileexists',
-	   'v16' => 'quoted',
-	   'v171' => 'regex',
-	   'v172' => 'regex',
-	   'v18' => 'novars',
-	   'v19' => 'ipv6',
-	   'v20' => 'ipv6',
-	   'v21' => 'ipv6',
-	   'v22' => 'ipv6',
-	   'v23' => 'ipv6',
+                   },
+           'item' => [ 'number' ],
+           'v1' => 'int',
+           'v2' => 'number',
+           'v3' => 'word',
+           'v4' => 'line',
+           'v5' => 'text',
+           'v6' => 'hostname',
+           'v8' => 'user',
+           'v10' => 'port',
+           'v11' => 'uri',
+           'v12' => 'cidrv4',
+           'v13' => 'ipv4',
+           'v14' => 'path',
+           'v15' => 'fileexists',
+           'v16' => 'quoted',
+           'v171' => 'regex',
+           'v172' => 'regex',
+           'v18' => 'novars',
+           'v19' => 'ipv6',
+           'v20' => 'ipv6',
+           'v21' => 'ipv6',
+           'v22' => 'ipv6',
+           'v23' => 'ipv6',
            'v24' => 'ipv6',
            'v25' => 'ipv6',
            'v26' => 'cidrv6',
@@ -48,54 +48,55 @@ my $ref = {
            'AoA' => [ [ 'int' ] ],
 
            'AoH' => [
-             { fullname => 'text', user => 'word', uid => 'int' }
-           ],
+                     {
+                      fullname => 'text', user => 'word', uid => 'int' }
+                    ],
 
            'HoH' => {
-             father   => { fullname => 'text', user => 'word' },
-             son      => { fullname => 'text', user => 'word' },
-             daughter => { fullname => 'text', user => 'word' },
-           },
+                     father   => { fullname => 'text', user => 'word' },
+                     son      => { fullname => 'text', user => 'word' },
+                     daughter => { fullname => 'text', user => 'word' },
+                    },
 
-	   'r1' => 'range(80-90)',
-	  };
+           'r1' => 'range(80-90)',
+          };
 
 my $cfg =  {
-	    'b1' => {
-		     'b2' => {
+            'b1' => {
+                     'b2' => {
                               'b3' => {
-				       'item' => '100'
+                                       'item' => '100'
                                       }
-			     }
-		    },
-	    'item' => [
-		       '10',
-		       '20',
-		       '30'
-		      ],
-	    'v1' => '123',
-	    'v2' => '19.03',
-	    'v3' => 'Johannes',
-	    'v4' => 'this is a line of text',
-	    'v5' => 'This is a text block
+                             }
+                    },
+            'item' => [
+                       '10',
+                       '20',
+                       '30'
+                      ],
+            'v1' => '123',
+            'v2' => '19.03',
+            'v3' => 'Johannes',
+            'v4' => 'this is a line of text',
+            'v5' => 'This is a text block
                      This is a text block',
-	    'v6' => 'search.cpan.org',
-	    'v8' => 'root',
-	    'v10' => '22',
-	    'v11' => 'http://search.cpan.org/~tlinden/?ignore&not=1',
-	    'v12' => '192.168.1.101/18',
-	    'v13' => '10.0.0.193',
-	    'v14' => '/etc/ssh/sshd.conf',
-	    'v15' => 'MANIFEST',
-	    'v16' => '\' this is a quoted string \'',
-	    'v171' => qr([0-9]+),
-	    'v172' => 'qr([0-9]+)',
-	    'v18' => 'Doesnt contain any variables',
-	    'v19' => '3ffe:1900:4545:3:200:f8ff:fe21:67cf',
-	    'v20' => 'fe80:0:0:0:200:f8ff:fe21:67cf',
-	    'v21' => 'fe80::200:f8ff:fe21:67cf',
-	    'v22' => 'ff02:0:0:0:0:0:0:1',
-	    'v23' => 'ff02::1',
+            'v6' => 'search.cpan.org',
+            'v8' => 'root',
+            'v10' => '22',
+            'v11' => 'http://search.cpan.org/~tlinden/?ignore&not=1',
+            'v12' => '192.168.1.101/18',
+            'v13' => '10.0.0.193',
+            'v14' => '/etc/ssh/sshd.conf',
+            'v15' => 'MANIFEST',
+            'v16' => '\' this is a quoted string \'',
+            'v171' => qr([0-9]+),
+            'v172' => 'qr([0-9]+)',
+            'v18' => 'Doesnt contain any variables',
+            'v19' => '3ffe:1900:4545:3:200:f8ff:fe21:67cf',
+            'v20' => 'fe80:0:0:0:200:f8ff:fe21:67cf',
+            'v21' => 'fe80::200:f8ff:fe21:67cf',
+            'v22' => 'ff02:0:0:0:0:0:0:1',
+            'v23' => 'ff02::1',
             'v24' => '::ffff:192.0.2.128',
             'v25' => '::',
             'v26' => '2001:db8:dead:beef::b00c/64',
@@ -104,228 +105,234 @@ my $cfg =  {
             'v28' => '$ten',
 
             'AoA' => [
-              [ qw{ 10 11 12 13 } ],
-              [ qw{ 20 21 22 23 } ],
-              [ qw{ 30 31 32 33 } ],
-            ],
+                      [ qw{ 10 11 12 13 } ],
+                      [ qw{ 20 21 22 23 } ],
+                      [ qw{ 30 31 32 33 } ],
+                     ],
 
             'AoH' => [
-              { fullname => 'Homer Simpson', user => 'homer', uid => 100 },
-              { fullname => 'Bart Simpson',  user => 'bart',  uid => 101 },
-              { fullname => 'Lisa Simpson',  user => 'lisa',  uid => 102 },
-            ],
+                      {
+                       fullname => 'Homer Simpson', user => 'homer', uid => 100 },
+                      {
+                       fullname => 'Bart Simpson',  user => 'bart',  uid => 101 },
+                      {
+                       fullname => 'Lisa Simpson',  user => 'lisa',  uid => 102 },
+                     ],
 
             'HoH' => {
-              father =>   { fullname => 'Homer Simpson', user => 'homer' },
-              son =>      { fullname => 'Bart Simpson',  user => 'bart'  },
-              daughter => { fullname => 'Lisa Simpson',  user => 'lisa'  },
-            },
+                      father =>   { fullname => 'Homer Simpson', user => 'homer' },
+                      son =>      { fullname => 'Bart Simpson',  user => 'bart'  },
+                      daughter => { fullname => 'Lisa Simpson',  user => 'lisa'  },
+                     },
 
-	    'r1' => 85,
-	   };
+            'r1' => 85,
+           };
 
 my $v = new_ok('Data::Validate::Struct', [ $ref ]);
 ok ($v->validate($cfg), "validate a reference against a OK config");
 
 
-
 # check failure matching
 my @failure = (
- {
-   cfg  => q(acht),
-   type => q(int),
-   descr => 'int',
-   errors => 1,
- },
+               {
+                cfg  => q(acht),
+                type => q(int),
+                descr => 'int',
+                errors => 1,
+               },
 
- {
-   cfg  => q(27^8),
-   type => q(number),
-   descr => 'number',
-   errors => 1,
- },
+               {
+                cfg  => q(27^8),
+                type => q(number),
+                descr => 'number',
+                errors => 1,
+               },
 
- {
-   cfg  => q(two words),
-   type => q(word),
-   descr => 'word',
-   errors => 1,
- },
+               {
+                cfg  => q(two words),
+                type => q(word),
+                descr => 'word',
+                errors => 1,
+               },
 
- {
-   cfg  => qq(<<EOF\nzeile1\nzeile2\nzeile3\nEOF\n),
-   type => q(line),
-   descr => 'line',
-   errors => 1,
- },
+               {
+                cfg  => qq(<<EOF\nzeile1\nzeile2\nzeile3\nEOF\n),
+                type => q(line),
+                descr => 'line',
+                errors => 1,
+               },
 
- {
-   cfg  => q(ätz),
-   type => q(hostname),
-   descr => 'hostname',
-   errors => 1,
- },
+               {
+                cfg  => q(ätz),
+                type => q(hostname),
+                descr => 'hostname',
+                errors => 1,
+               },
 
- {
-   cfg  => q(gibtsnet123456790.intern),
-   type => q(resolvablehost),
-   descr => 'resolvablehost',
-   errors => 1,
- },
+               {
+                cfg  => q(gibtsnet123456790.intern),
+                type => q(resolvablehost),
+                descr => 'resolvablehost',
+                errors => 1,
+               },
 
- {
-   cfg  => q(äüö),
-   type => q(user),
-   descr => 'user',
-   errors => 1,
- },
+               {
+                cfg  => q(äüö),
+                type => q(user),
+                descr => 'user',
+                errors => 1,
+               },
 
- {
-   cfg  => q(äüö),
-   type => q(group),
-   descr => 'group',
-   errors => 1,
- },
+               {
+                cfg  => q(äüö),
+                type => q(group),
+                descr => 'group',
+                errors => 1,
+               },
 
- {
-   cfg  => q(234234444),
-   type => q(port),
-   descr => 'port',
-   errors => 1,
- },
+               {
+                cfg  => q(234234444),
+                type => q(port),
+                descr => 'port',
+                errors => 1,
+               },
 
- {
-   cfg  => q(unknown:/unsinnüäö),
-   type => q(uri),
-   descr => 'uri',
-   errors => 1,
- },
+               {
+                cfg  => q(unknown:/unsinnüäö),
+                type => q(uri),
+                descr => 'uri',
+                errors => 1,
+               },
 
- {
-   cfg  => q(1.1.1.1/33),
-   type => q(cidrv4),
-   descr => 'cidrv4',
-   errors => 1,
- },
+               {
+                cfg  => q(1.1.1.1/33),
+                type => q(cidrv4),
+                descr => 'cidrv4',
+                errors => 1,
+               },
 
- {
-   cfg  => q(300.1.1.1),
-   type => q(ipv4),
-   descr => 'ipv4',
-   errors => 1,
- },
+               {
+                cfg  => q(300.1.1.1),
+                type => q(ipv4),
+                descr => 'ipv4',
+                errors => 1,
+               },
 
- {
-   cfg  => q(üäö),
-   type => q(fileexists),
-   descr => 'fileexists',
-   errors => 1,
- },
+               {
+                cfg  => q(üäö),
+                type => q(fileexists),
+                descr => 'fileexists',
+                errors => 1,
+               },
 
- {
-   cfg  => q(not quoted),
-   type => q(quoted),
-   descr => 'quoted',
-   errors => 1,
- },
+               {
+                cfg  => q(not quoted),
+                type => q(quoted),
+                descr => 'quoted',
+                errors => 1,
+               },
 
- {
-   cfg  => q(no regex),
-   type => q(regex),
-   descr => 'regex',
-   errors => 1,
- },
+               {
+                cfg  => q(no regex),
+                type => q(regex),
+                descr => 'regex',
+                errors => 1,
+               },
 
- {
-   cfg  => q($contains some $vars),
-   type => q(novars),
-   descr => 'novars',
-   errors => 1,
- },
+               {
+                cfg  => q($contains some $vars),
+                type => q(novars),
+                descr => 'novars',
+                errors => 1,
+               },
 
- {
-   cfg  => q(2001:db8::dead::beef),
-   type => q(ipv6),
-   descr => 'ipv6',
-   errors => 1,
- },
+               {
+                cfg  => q(2001:db8::dead::beef),
+                type => q(ipv6),
+                descr => 'ipv6',
+                errors => 1,
+               },
 
- {
-   cfg  => q(2001:db8:dead:beef::1/129),
-   type => q(cidrv6),
-   descr => 'cidrv6',
-   errors => 1,
- },
+               {
+                cfg  => q(2001:db8:dead:beef::1/129),
+                type => q(cidrv6),
+                descr => 'cidrv6',
+                errors => 1,
+               },
 
- {
-   cfg => [
-     [ qw{ 10 11 12 13 } ],
-     [ qw{ 'twenty' 21 22 23 } ],
-     [ qw{ 30 31 32.0 33 } ],
-   ],
+               {
+                cfg => [
+                        [ qw{ 10 11 12 13 } ],
+                        [ qw{ 'twenty' 21 22 23 } ],
+                        [ qw{ 30 31 32.0 33 } ],
+                       ],
 
-   type => [ [ 'int' ] ],
+                type => [ [ 'int' ] ],
 
-   descr => 'array of arrays',
-   errors => 2,
- },
+                descr => 'array of arrays',
+                errors => 2,
+               },
 
- {
-   cfg => [
-    { fullname => 'Homer Simpson', user => 'homer', uid => 100 },
-    { fullname => 'Bart Simpson',  user => ':bart',  uid => 101 },
-    { fullname => 'Lisa Simpson',  user => 'lisa',  uid => '102' },
-   ],
+               {
+                cfg => [
+                        {
+                         fullname => 'Homer Simpson', user => 'homer', uid => 100 },
+                        {
+                         fullname => 'Bart Simpson',  user => ':bart',  uid => 101 },
+                        {
+                         fullname => 'Lisa Simpson',  user => 'lisa',  uid => '102' },
+                       ],
 
-   type => [
-     { fullname => 'text', user => 'word', uid => 'int' }
-   ],
+                type => [
+                         {
+                          fullname => 'text', user => 'word', uid => 'int' }
+                        ],
 
-   descr => 'array of hashes',
-   errors => 1,
- },
+                descr => 'array of hashes',
+                errors => 1,
+               },
 
- {
-   cfg => {
-    father   => { fullname => 'Homer Simpson', user => 'homer', uid => 100 },
-    son      => { fullname => 'Bart Simpson',  user => 'bart',  uid => 'one hundred one' },
-    daughter => { fullname => 'Lisa Simpson',  user => 'lisa:', uid => 'one hundred two' },
-  },
+               {
+                cfg => {
+                        father   => { fullname => 'Homer Simpson', user => 'homer', uid => 100 },
+                        son      => { fullname => 'Bart Simpson',  user => 'bart',  uid => 'one hundred one' },
+                        daughter => { fullname => 'Lisa Simpson',  user => 'lisa:', uid => 'one hundred two' },
+                       },
 
-   type => {
-     father   => { fullname => 'text', user => 'word', uid => 'int' },
-     son      => { fullname => 'text', user => 'word', uid => 'int' },
-     daughter => { fullname => 'text', user => 'word', uid => 'int' },
-   },
+                type => {
+                         father   => { fullname => 'text', user => 'word', uid => 'int' },
+                         son      => { fullname => 'text', user => 'word', uid => 'int' },
+                         daughter => { fullname => 'text', user => 'word', uid => 'int' },
+                        },
 
-   descr => 'hash of hashes',
-   errors => 3,
- },
+                descr => 'hash of hashes',
+                errors => 3,
+               },
 
- {
-    cfg => {
-      name    => 'Foo Bar',
-      age     => 42,
-    },
+               {
+                cfg => {
+                        name    => 'Foo Bar',
+                        age     => 42,
+                       },
 
-    type => {
-      name    => 'text',
-      age     => 'int',
-      address => 'text',
-    },
+                type => {
+                         name    => 'text',
+                         age     => 'int',
+                         address => 'text',
+                        },
 
-   descr => 'Missing required field',
-   errors => 1,
- },
+                descr => 'Missing required field',
+                errors => 1,
+               },
 
- {
-  cfg => 100,
-  type => 'range(200-1000)',
-  descr => 'value outside dynamic range',
-  errors => 1,
- },
+               {
+                cfg => 100,
+                type => 'range(200-1000)',
+                descr => 'value outside dynamic range',
+                errors => 1,
+               },
 
-);
+              );
 
 foreach my $test (@failure) {
   my $ref    = { v => $test->{type} };
@@ -334,13 +341,12 @@ foreach my $test (@failure) {
   #$v->debug();
   my $result = $v->validate($cfg);
   my $descr = encode('UTF-8',
-    exists $test->{descr} ? $test->{descr} : $test->{cfg}
-  );
+                     exists $test->{descr} ? $test->{descr} : $test->{cfg}
+                    );
   my $errors = exists $test->{errors} ? $test->{errors} : 1;
   unless ($result) {
     is @{$v->errors}, $errors, "Caught failure for '$descr'";
-  }
-  else {
+  } else {
     fail("Couldn't catch invalid '$test->{descr}'");
   }
 }
@@ -349,45 +355,45 @@ foreach my $test (@failure) {
 # clean old object
 undef $v;
 $v = Data::Validate::Struct->new({
-  h1 => { h2 => { item => 'int' } }
-});
+                                  h1 => { h2 => { item => 'int' } }
+                                 });
 ok !$v->validate({
-  h1 => { h2 => { item => 'qux' } }
-}), 'item is not an h1 => h2 => int';
+                  h1 => { h2 => { item => 'qux' } }
+                 }), 'item is not an h1 => h2 => int';
 is $v->errstr, q{'qux' doesn't match 'int' at 'h1 => h2'}, 'correct error trace';
 
 
 # adding custom type
 my $ref3 = {
-  v1 => 'address',
-  v2 => 'list',
-  v3 => 'noob',
-  v4 => 'nonoob',
-};
+            v1 => 'address',
+            v2 => 'list',
+            v3 => 'noob',
+            v4 => 'nonoob',
+           };
 my $cfg3 = {
-  v1 => 'Marblestreet 15',
-  v2 => 'a1, b2, b3',
-  v3 => 42,
-  v4 => 43,
-};
+            v1 => 'Marblestreet 15',
+            v2 => 'a1, b2, b3',
+            v3 => 42,
+            v4 => 43,
+           };
 
 my $v3 = new Data::Validate::Struct($ref3);
 # add via hash
 note('added via hash');
 my %h = (
-  address => qr(^\w+\s\s*\d+$)
-);
+         address => qr(^\w+\s\s*\d+$)
+        );
 $v3->type(%h);
 
 # add via hash ref
 note('added via hash ref');
 $v3->type({ list =>
-  sub {
-    my $list = $_[0];
-    my @list = split /\s*,\s*/, $list;
-    return scalar @list > 1;
-  }
-});
+            sub {
+              my $list = $_[0];
+              my @list = split /\s*,\s*/, $list;
+              return scalar @list > 1;
+            }
+          });
 
 # add via key => value
 note('added via key => val');
@@ -401,9 +407,30 @@ my $v4 = Data::Validate::Struct->new({age => 'int'});
 ok(!$v4->validate({age => 'eight'}), "cache check first run, error");
 ok($v4->validate({age => 8}), "cache check second run, no error");
 
-# different references
-my $v5 = Data::Validate::Struct->new({ foo => [{bar => 'int'}]});
-ok(!$v5->validate({foo=>{bar=>10}}));
-
+# optional array, see:
+# https://github.com/TLINDEN/Data-Validate-Struct/issues/7
+my $ref4 = {
+            routers => [ {
+                          stubs => [ {
+                                      network => 'ipv4',
+                                     }, {} ],
+                         }, {}, ],
+           };
+my $test4 = {
+               'routers' => [
+                             {
+                              'stubs' => [
+                                          {
+                                           'network' => '172.31.199.0',
+                                          }
+                                         ],
+                              'router' => '172.31.199.2', # optional, ignored by validate
+                             },
+                             { # optional as well
+                              'router' => '172.30.5.5',
+                             },
+                            ],
+              };
+my $v4 = Data::Validate::Struct->new($ref4);
+ok($v4->validate($test4), "check optional " . $Data::Validate::Struct::VERSION);
 done_testing();
-