diff --git a/Lib/bdb.py b/Lib/bdb.py
--- a/Lib/bdb.py
+++ b/Lib/bdb.py
@@ -70,7 +70,10 @@
         # XXX 'arg' is no longer used
         if self.botframe is None:
             # First call of dispatch since reset()
-            self.botframe = frame.f_back # (CT) Note that this may also be None!
+            # Note that frame may be a debugger frame. The derived class must
+            # ensure that self.botframe is a debuggee frame and not a debugger
+            # frame.
+            self.botframe = frame
             return self.trace_dispatch
         if not (self.stop_here(frame) or self.break_anywhere(frame)):
             # No need to trace this function
diff --git a/Lib/pdb.py b/Lib/pdb.py
--- a/Lib/pdb.py
+++ b/Lib/pdb.py
@@ -193,9 +193,10 @@
             raise KeyboardInterrupt
         self.message("\nProgram interrupted. (Use 'cont' to resume).")
         self.set_step()
-        self.set_trace(frame)
         # restore previous signal handler
         signal.signal(signal.SIGINT, self._previous_sigint_handler)
+        frame.f_trace = self.trace_dispatch
+        sys.settrace(self.trace_dispatch)
 
     def reset(self):
         bdb.Bdb.reset(self)
@@ -261,6 +262,7 @@
             if (self.mainpyfile != self.canonic(frame.f_code.co_filename)
                 or frame.f_lineno <= 0):
                 return
+            self.botframe = frame
             self._wait_for_mainpyfile = False
         if self.bp_commands(frame):
             self.interaction(frame, None)
diff --git a/Lib/test/test_pdb.py b/Lib/test/test_pdb.py
--- a/Lib/test/test_pdb.py
+++ b/Lib/test/test_pdb.py
@@ -3,14 +3,20 @@
 import imp
 import pdb
 import sys
+import signal
 import unittest
 import subprocess
 import textwrap
+try:
+    import threading
+except ImportError:
+    threading = None
 
 from test import support
 # This little helper class is essential for testing pdb under doctest.
 from test.test_doctest import _FakeInput
 
+mswindows = (sys.platform == "win32")
 
 class PdbTestInput(object):
     """Context manager that makes testing Pdb in doctests easier."""
@@ -599,7 +605,7 @@
 
 class PdbTestCase(unittest.TestCase):
 
-    def run_pdb(self, script, commands):
+    def run_pdb(self, script, commands, sigint=False):
         """Run 'script' lines with pdb and the pdb 'commands'."""
         filename = 'main.py'
         with open(filename, 'w') as f:
@@ -611,6 +617,14 @@
                                    stdin=subprocess.PIPE,
                                    stderr=subprocess.STDOUT,
                                    ) as proc:
+            # Interrupt the spawned process.
+            if threading and sigint:
+                def kill():
+                    # Wait for the subprocess to be fully started before
+                    # sending the signal.
+                    import time; time.sleep(1)
+                    proc.send_signal(signal.SIGINT)
+                threading.Thread(target=kill).start()
             stdout, stderr = proc.communicate(str.encode(commands))
         stdout = stdout and bytes.decode(stdout)
         stderr = stderr and bytes.decode(stderr)
@@ -667,6 +681,57 @@
             any('main.py(5)foo()->None' in l for l in stdout.splitlines()),
             'Fail to step into the caller after a return')
 
+    def test_issue_14743_1(self):
+        script = "x = 1"
+        commands = """
+            step
+            step
+            quit
+        """
+        stdout, stderr = self.run_pdb(script, commands)
+        self.assertTrue(
+            any('The program finished and will be restarted'
+                    in l for l in stdout.splitlines()),
+            'Debugging session not terminated after returning from initial'
+            ' user frame.')
+
+    @unittest.skipIf(mswindows or not threading, "posix with threads test")
+    def test_issue_14743_2(self):
+        script = """
+            import bar
+
+            def foo():
+                bar.bar()
+
+            foo()
+            pass # for setting the breakpoint
+        """
+        commands = """
+            break 8
+            continue
+            !i=0
+            continue
+            step
+            step
+            quit
+        """
+        bar = """
+            import time
+            def bar():
+                i = 1
+                while i:
+                    time.sleep(.100)
+        """
+        with open('bar.py', 'w') as f:
+            f.write(textwrap.dedent(bar))
+        self.addCleanup(support.unlink, 'bar.py')
+        stdout, stderr = self.run_pdb(script, commands, sigint=True)
+        self.assertTrue(
+            any('The program finished and will be restarted'
+                    in l for l in stdout.splitlines()),
+            'Interrupted debugging session not terminated after returning'
+            ' from initial user frame.')
+
     def tearDown(self):
         support.unlink(support.TESTFN)