diff --git a/Lib/test/test_sys_settrace.py b/Lib/test/test_sys_settrace.py
--- a/Lib/test/test_sys_settrace.py
+++ b/Lib/test/test_sys_settrace.py
@@ -232,6 +232,20 @@
                             [(5, 'line'), (6, 'line')] * 10 +
                             [(5, 'line'), (5, 'return')])
 
+def _settrace_at_return(tracefunc):
+    sys.settrace(tracefunc)
+    sys._getframe().f_back.f_trace = tracefunc
+    return True
+def settrace_at_return(tracefunc):
+    a = 1
+    while a:
+        x = 1
+        if _settrace_at_return(tracefunc): break
+    else:
+        x = 2
+
+settrace_at_return.events = [(4, 'return')]
+
 
 class Tracer:
     def __init__(self):
@@ -243,6 +257,18 @@
         (o for o in [1])
         self.events.append((frame.f_lineno, event))
         return self.trace
+    def traceSetNone(self, frame, event, arg):
+        if event == 'line':
+            if frame.f_code.co_name == 'set_none':
+                sys.settrace(None)
+                while frame:
+                    del frame.f_trace
+                    frame = frame.f_back
+                return None
+            elif frame.f_code.co_name == 'set_none_keep_f_trace':
+                sys.settrace(None)
+                return None
+        return self.traceSetNone
 
 class TraceTestCase(unittest.TestCase):
 
@@ -297,6 +323,35 @@
         finally:
             sys.settrace(None)
 
+    def test_set_none_generator(self):
+        # Issue17277: set trace None while a generator is suspended.
+        def gen():
+            yield 1
+            self.assertEqual(sys._getframe().f_lineno
+                             - gen.__code__.co_firstlineno, 2)
+            yield 2
+
+        def set_none():
+            pass
+
+        sys.settrace(Tracer().traceSetNone)
+        it = gen()
+        next(it)
+        set_none()
+        next(it)
+
+    def test_set_none(self):
+        # Issue17697: set trace None without deleting f_trace of the frames on
+        # the stack.
+        def set_none_keep_f_trace():
+            x = 1
+            self.assertEqual(sys._getframe().f_lineno
+                             - set_none_keep_f_trace.__code__.co_firstlineno,
+                             2)
+
+        sys.settrace(Tracer().traceSetNone)
+        set_none_keep_f_trace()
+
     def test_01_basic(self):
         self.run_test(basic)
     def test_02_arigo(self):
@@ -388,6 +443,11 @@
              (257, 'line'),
              (257, 'return')])
 
+    def test_17_settrace_at_return(self):
+        # Tracing is set while the next tracing event for a frame on the stack
+        # is a "return" event.
+        self.run_test2(settrace_at_return)
+
 
 class RaisingTraceFuncTestCase(unittest.TestCase):
     def setUp(self):