diff --git a/core/kernel/sleep_spec.rb b/core/kernel/sleep_spec.rb
index 08c79830a..9081c5448 100644
--- a/core/kernel/sleep_spec.rb
+++ b/core/kernel/sleep_spec.rb
@@ -59,6 +59,7 @@ def o.divmod(*); [0, 0.001]; end
     end_time = Process.clock_gettime(Process::CLOCK_MONOTONIC)
 
     actual_duration = end_time - start_time
+    puts "start: #{start_time}, end: #{end_time}, actual: #{actual_duration}"
     (actual_duration > 0.01).should == true # 100 * 0.0001 => 0.01
     (actual_duration < 0.03).should == true
   end