diff --git a/lib/mutant/isolation.rb b/lib/mutant/isolation.rb
index 066b9025..7b29eff6 100644
--- a/lib/mutant/isolation.rb
+++ b/lib/mutant/isolation.rb
@@ -38,9 +38,7 @@ module Mutant
       # @api private
       #
       def self.call(&block)
-        Parallel.map([block], in_processes: 1) do
-          block.call
-        end.first
+        Parallel.map([block], in_processes: 1, &block.method(:call)).first
       rescue Parallel::DeadWorker => exception
         fail Error, exception
       end