diff --git a/Changelog b/Changelog
index 1e676b5..7d84482 100644
--- a/Changelog
+++ b/Changelog
@@ -1,3 +1,6 @@
+0.13
+    o rework commit 495fcbc
+
 0.12
 	o revert commit 495fcbc, see #7: breaks backwards
 	  compatibility.
diff --git a/Struct.pm b/Struct.pm
index 951391f..91faccb 100644
--- a/Struct.pm
+++ b/Struct.pm
@@ -196,21 +196,30 @@ sub _traverse {
 
   foreach my $key (keys %{$reference}) {
     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)) {
-          # traverse the structure pushing our key to the @tree
-          $self->_traverse($reference->{$key}->[0], $item, @tree, $key);
-        }
-        else {
-          # a value, this is tricky
-          $self->_traverse(
-            { item => $reference->{$key}->[0] },
-            { item => $item },
-            @tree, $key
-          );
+
+      # either it is undefined (optional values)
+      # or it should be an array, so we can derreference it.
+      if (!defined($hash->{$key}) || ref($hash->{$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)) {
+            # traverse the structure pushing our key to the @tree
+            $self->_traverse($reference->{$key}->[0], $item, @tree, $key);
+          }
+          else {
+            # a value, this is tricky
+            $self->_traverse(
+              { item => $reference->{$key}->[0] },
+              { item => $item },
+              @tree, $key
+            );
+          }
         }
       }
+      else {
+        push @{$self->{errors}}, "$key is not an array";
+      }
     }
     elsif (ref($reference->{$key}) eq 'HASH') {
       $self->_traverse($reference->{$key}, $hash->{$key}, @tree, $key);
diff --git a/t/run.t b/t/run.t
index 697ee34..c319ed7 100644
--- a/t/run.t
+++ b/t/run.t
@@ -409,14 +409,14 @@ ok($v4->validate({age => 8}), "cache check second run, no error");
 
 # optional array, see:
 # https://github.com/TLINDEN/Data-Validate-Struct/issues/7
-my $ref4 = {
+my $ref5 = {
             routers => [ {
                           stubs => [ {
                                       network => 'ipv4',
                                      }, {} ],
                          }, {}, ],
            };
-my $test4 = {
+my $test5 = {
                'routers' => [
                              {
                               'stubs' => [
@@ -431,6 +431,11 @@ my $test4 = {
                              },
                             ],
               };
-my $v4 = Data::Validate::Struct->new($ref4);
-ok($v4->validate($test4), "check optional " . $Data::Validate::Struct::VERSION);
+my $v5 = Data::Validate::Struct->new($ref5);
+ok($v5->validate($test5), "check optional " . $Data::Validate::Struct::VERSION);
+
+# different references
+my $v6 = Data::Validate::Struct->new({ foo => [{bar => 'int'}]});
+ok(!$v6->validate({foo=>{bar=>10}}));
+
 done_testing();