diff --git a/Lib/trace.py b/Lib/trace.py
--- a/Lib/trace.py
+++ b/Lib/trace.py
@@ -503,14 +503,12 @@
         import __main__
         dict = __main__.__dict__
         if not self.donothing:
-            threading.settrace(self.globaltrace)
-            sys.settrace(self.globaltrace)
+            _settrace(self.globaltrace)
         try:
             exec cmd in dict, dict
         finally:
             if not self.donothing:
-                sys.settrace(None)
-                threading.settrace(None)
+                _unsettrace()
 
     def runctx(self, cmd, globals=None, locals=None):
         if globals is None: globals = {}