diff --git a/lib/mutant/context/scope.rb b/lib/mutant/context/scope.rb
index 0ad28624..b06c2b34 100644
--- a/lib/mutant/context/scope.rb
+++ b/lib/mutant/context/scope.rb
@@ -96,7 +96,10 @@ module Mutant
       # @api private
       #
       def match_prefixes
-        name_nesting.reverse
+        names = name_nesting
+        names.length.downto(1).map do |last|
+          names[0...last].join('::')
+        end
       end
       memoize :match_prefixes
 
diff --git a/lib/mutant/subject.rb b/lib/mutant/subject.rb
index 19c62f6e..f032a24e 100644
--- a/lib/mutant/subject.rb
+++ b/lib/mutant/subject.rb
@@ -99,7 +99,7 @@ module Mutant
     # @api private
     #
     def match_prefixes
-      context.match_prefixes.dup << match_expression
+      [match_expression].concat(context.match_prefixes)
     end
     memoize :match_prefixes