diff --git a/Gemfile.lock b/Gemfile.lock
index 376a5ed..cbfdc83 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -1,7 +1,7 @@
 PATH
   remote: .
   specs:
-    openlib (0.1.1)
+    openlib (0.1.2)
 
 GEM
   remote: https://rubygems.org/
diff --git a/lib/openlib/book.rb b/lib/openlib/book.rb
index 6820f2b..2d426b8 100644
--- a/lib/openlib/book.rb
+++ b/lib/openlib/book.rb
@@ -37,7 +37,7 @@ module Openlib
 
     def data_data(req:)
       case req
-      when :authors, :publishers, :subjects then data.dig(req.to_s).map { |p| p.dig('name') }
+      when :authors, :publishers, :subjects then data.dig(req.to_s)&.map { |p| p.dig('name') }
       else
         data.dig(req.to_s)
       end
diff --git a/lib/openlib/version.rb b/lib/openlib/version.rb
index fc3b73b..772ba9d 100644
--- a/lib/openlib/version.rb
+++ b/lib/openlib/version.rb
@@ -1,3 +1,3 @@
 module Openlib
-  VERSION = "0.1.2"
+  VERSION = "0.1.3"
 end