diff --git a/AUTHORS b/AUTHORS
index 043de70c1b4..c74aa4af685 100644
--- a/AUTHORS
+++ b/AUTHORS
@@ -91,6 +91,7 @@ Martin Prusse
 Matt Bachmann
 Matt Williams
 Matthias Hafner
+mbyt
 Michael Aquilina
 Michael Birtwell
 Michael Droettboom
diff --git a/CHANGELOG.rst b/CHANGELOG.rst
index 5689d04dc91..44fc9f25924 100644
--- a/CHANGELOG.rst
+++ b/CHANGELOG.rst
@@ -18,15 +18,23 @@
   if a test suite uses ``pytest_plugins`` to load internal plugins (`#1888`_).
   Thanks `@jaraco`_ for the report and `@nicoddemus`_ for the PR (`#1891`_).
 
+* Do not call tearDown and cleanups when running tests from
+  ``unittest.TestCase`` subclasses with ``--pdb``
+  enabled. This allows proper post mortem debugging for all applications
+  which have significant logic in their tearDown machinery (`#1890`_). Thanks
+  `@mbyt`_ for the PR.
+
 *
 
 .. _@joguSD: https://github.com/joguSD
 .. _@AiOO: https://github.com/AiOO
+.. _@mbyt: https://github.com/mbyt
 
 .. _#1857: https://github.com/pytest-dev/pytest/issues/1857
 .. _#1864: https://github.com/pytest-dev/pytest/issues/1864
 .. _#1888: https://github.com/pytest-dev/pytest/issues/1888
 .. _#1891: https://github.com/pytest-dev/pytest/pull/1891
+.. _#1890: https://github.com/pytest-dev/pytest/issues/1890
 
 
 3.0.1
diff --git a/_pytest/unittest.py b/_pytest/unittest.py
index f24b496242a..47868f4483c 100644
--- a/_pytest/unittest.py
+++ b/_pytest/unittest.py
@@ -150,7 +150,12 @@ def stopTest(self, testcase):
         pass
 
     def runtest(self):
-        self._testcase(result=self)
+        if self.config.pluginmanager.get_plugin("pdbinvoke") is None:
+            self._testcase(result=self)
+        else:
+            # disables tearDown and cleanups for post mortem debugging (see #1890)
+            self._testcase.debug()
+
 
     def _prunetraceback(self, excinfo):
         pytest.Function._prunetraceback(self, excinfo)
diff --git a/doc/en/unittest.rst b/doc/en/unittest.rst
index 9e0b4973d43..d400adcaa3d 100644
--- a/doc/en/unittest.rst
+++ b/doc/en/unittest.rst
@@ -33,6 +33,13 @@ distributing tests to multiple CPUs via the ``-nNUM`` option if you
 installed the ``pytest-xdist`` plugin.  Please refer to
 the general ``pytest`` documentation for many more examples.
 
+.. note::
+
+    Running tests from ``unittest.TestCase`` subclasses with ``--pdb`` will
+    disable tearDown and cleanup methods for the case that an Exception
+    occurs. This allows proper post mortem debugging for all applications
+    which have significant logic in their tearDown machinery.
+
 Mixing pytest fixtures into unittest.TestCase style tests
 -----------------------------------------------------------
 
diff --git a/testing/test_pdb.py b/testing/test_pdb.py
index 6e4f3e80582..d79d7126209 100644
--- a/testing/test_pdb.py
+++ b/testing/test_pdb.py
@@ -79,6 +79,25 @@ def test_1():
         if child.isalive():
             child.wait()
 
+    def test_pdb_unittest_postmortem(self, testdir):
+        p1 = testdir.makepyfile("""
+            import unittest
+            class Blub(unittest.TestCase):
+                def tearDown(self):
+                    self.filename = None
+                def test_false(self):
+                    self.filename = 'debug' + '.me'
+                    assert 0
+        """)
+        child = testdir.spawn_pytest("--pdb %s" % p1)
+        child.expect('(Pdb)')
+        child.sendline('p self.filename')
+        child.sendeof()
+        rest = child.read().decode("utf8")
+        assert 'debug.me' in rest
+        if child.isalive():
+            child.wait()
+
     def test_pdb_interaction_capture(self, testdir):
         p1 = testdir.makepyfile("""
             def test_1():