diff --git a/test/lib/minitest/unit.rb b/test/lib/minitest/unit.rb
index fa79b3bcf5..b084318bb1 100644
--- a/test/lib/minitest/unit.rb
+++ b/test/lib/minitest/unit.rb
@@ -1020,6 +1020,7 @@ module MiniTest
       @verbose = false
       @mutex = Thread::Mutex.new
       @info_signal = Signal.list['INFO']
+      @repeat_count = nil
     end
 
     def synchronize # :nodoc: