diff --git a/test/unit/support/shared/base_context.rb b/test/unit/support/shared/base_context.rb
index ff719bb81..f0fc4efb0 100644
--- a/test/unit/support/shared/base_context.rb
+++ b/test/unit/support/shared/base_context.rb
@@ -80,6 +80,7 @@ shared_context "unit" do
     # Create a temporary directory and append it to the instance
     # variabe so that it isn't garbage collected and deleted
     d = Dir.mktmpdir("vagrant")
+    @_temp_files ||= []
     @_temp_files << d
 
     # Return the pathname