diff --git a/lib/vcr/version.rb b/lib/vcr/version.rb
index 0233d7ed..0d8f59e6 100644
--- a/lib/vcr/version.rb
+++ b/lib/vcr/version.rb
@@ -10,7 +10,7 @@ module VCR
   #   * `parts` [Array<Integer>] List of the version parts.
   def version
     @version ||= begin
-      string = '6.0.0'
+      string = +'6.0.0'
 
       def string.parts
         split('.').map { |p| p.to_i }
@@ -28,7 +28,7 @@ def string.patch
         parts[2]
       end
 
-      string
+      string.freeze
     end
   end
 end