diff --git a/Lib/test/test_tcl.py b/Lib/test/test_tcl.py
index 1d90ac10ad77ade..f1953e4a2371173 100644
--- a/Lib/test/test_tcl.py
+++ b/Lib/test/test_tcl.py
@@ -596,6 +596,35 @@ def test_returning_deeply_nested(self):
                     % support.exceeds_recursion_limit())
         self.assertRaises(RecursionError, interp.getvar, 'x')
 
+    def test_setvar_evil(self):
+        # gh-161388
+        class StrRaises:
+            def __str__(self):
+                raise RuntimeError("setvar evil")
+
+        default = StrRaises()
+
+        for getvar, setvar, unsetvar in [
+            (
+                self.interp.tk.getvar,
+                self.interp.tk.setvar,
+                self.interp.tk.unsetvar,
+            ),
+            (
+                self.interp.tk.globalgetvar,
+                self.interp.tk.globalsetvar,
+                self.interp.tk.globalunsetvar,
+            )
+        ]:
+            with self.subTest(getvar=getvar, setvar=setvar, unsetvar=unsetvar):
+                with self.assertRaisesRegex(RuntimeError, "setvar evil"):
+                    setvar("name1", "name2", default)
+
+                self.assertRaises(TclError, getvar, "name1")
+                self.assertIsNone(setvar("name1", "name2"))
+                self.assertEqual(getvar("name1"), "name2")
+                self.assertIsNone(unsetvar("name1"))
+
     def test_user_command(self):
         result = None
         def testfunc(arg):
diff --git a/Modules/_tkinter.c b/Modules/_tkinter.c
index 9a09687e55b9817..70a10cea038348d 100644
--- a/Modules/_tkinter.c
+++ b/Modules/_tkinter.c
@@ -1234,8 +1234,9 @@ AsObjNested(PyObject *value, int depth)
 
     {
         PyObject *v = PyObject_Str(value);
-        if (!v)
-            return 0;
+        if (!v) {
+            return NULL;
+        }
         result = AsObjNested(v, depth);
         Py_DECREF(v);
         return result;
@@ -2101,6 +2102,9 @@ SetVar(TkappObject *self, PyObject *args, int flags)
 
         /* XXX must hold tcl lock already??? */
         newval = AsObj(newValue);
+        if (newval == NULL) {
+            return NULL;
+        }
         if (self->trace) {
             if (flags & TCL_GLOBAL_ONLY) {
                 TRACE(self, ("((sssNO))", "uplevel", "#0", "set",