diff --git a/Lib/test/test_tcl.py b/Lib/test/test_tcl.py
index a6e95e5718..6fa73d144f 100644
--- a/Lib/test/test_tcl.py
+++ b/Lib/test/test_tcl.py
@@ -386,6 +386,7 @@ class TclTest(unittest.TestCase):
             result.append(arg)
             return arg
         self.interp.createcommand('testfunc', testfunc)
+        self.addCleanup(self.interp.tk.deletecommand, 'testfunc')
         def check(value, expected, expected2=None, eq=self.assertEqual):
             if expected2 is None:
                 expected2 = expected
diff --git a/Misc/NEWS b/Misc/NEWS
index 2593500238..26c96c2d5e 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -249,6 +249,8 @@ IDLE
 Tests
 -----
 
+- Issue #20743: Fix a reference leak in test_tcl.
+
 - Issue #20510: Rewrote test_exit in test_sys to match existing comments,
   use modern unittest features, and use helpers from test.script_helper
   instead of using subprocess directly.  Initial patch by Gareth Rees.