1 files changed, 1 insertions, 1 deletions
diff --git a/lib/tracer.rb b/lib/tracer.rb
index fd45f003c8..24a5313f4c 100644
--- a/lib/tracer.rb
+++ b/lib/tracer.rb
@@ -91,7 +91,7 @@ class Tracer
   Tracer::display_thread_id = true
   Tracer::display_c_call = false
 
-  @stdout_mutex = Mutex.new
+  @stdout_mutex = Thread::Mutex.new
 
   # Symbol table used for displaying trace information
   EVENT_SYMBOL = {