diff --git a/Makefile.PL b/Makefile.PL
index 5f8ce4b..5327bbd 100644
--- a/Makefile.PL
+++ b/Makefile.PL
@@ -24,6 +24,7 @@ WriteMakefile(
         'Data::Compare' => '1.25',
         'Data::Dump'    => '1.23',
         'UUID::Tiny'    => '1.04',
+        'YAML::XS'      => '0.75',
     },
     TEST_REQUIRES       => {
         'Test::Pod'             => '1.52',
diff --git a/README.md b/README.md
index 48ebd21..010c3c4 100644
--- a/README.md
+++ b/README.md
@@ -41,6 +41,12 @@ $store->store_event(UserAdded => {id => 17, name => 'Bob'});
 say 'His name is ' . $store->snapshot->state->{users}{17}{name}; # Bob
 ```
 
+**ATTENTION**: From version 0.6 on the serialization format is changed from [Storable][] to [YAML][]. Use [convert_storable_to_yaml.pl][script] to use your old event store with newer versions.
+
+[Storable]: https://metacpan.org/pod/Storable
+[YAML]: https://metacpan.org/pod/YAML::XS
+[script]: convert_storable_to_yaml.pl
+
 ## Intro
 
 In Event Sourcing, the state of a system is calculated as the application of a stream of events representing each change of the system. This framework is a minimal approach to use these mechanics in simple perl systems.