diff --git a/Lib/test/regrtest.py b/Lib/test/regrtest.py
--- a/Lib/test/regrtest.py
+++ b/Lib/test/regrtest.py
@@ -1158,6 +1158,15 @@
         return self
 
     def __exit__(self, exc_type, exc_val, exc_tb):
+        if 'tkinter' in sys.modules:
+            sysmod = sys.modules
+            tknames = set()
+            for name in sysmod:
+                if name.startswith('tkinter'):
+                    tknames.add(name)
+            for name in tknames:
+                del sysmod[name]
+
         saved_values = self.saved_values
         del self.saved_values
         for name, get, restore in self.resource_info():