diff --git a/lib/mixlib/archive/tar.rb b/lib/mixlib/archive/tar.rb
index 30c8f9e..dcdb5b9 100644
--- a/lib/mixlib/archive/tar.rb
+++ b/lib/mixlib/archive/tar.rb
@@ -125,7 +125,7 @@ def is_tar_archive?(io)
 
       def read_tar_magic(io)
         io.rewind
-        magic = io.read(512).bytes[257..264].pack("C*")
+        magic = Array(io.read(512).bytes[257..264]).pack("C*")
         io.rewind
         magic
       end