diff --git a/AUTHORS b/AUTHORS
index e3bbdc5d1..acf715cde 100644
--- a/AUTHORS
+++ b/AUTHORS
@@ -141,3 +141,4 @@ Tyler Goodlet
 Vasily Kuznetsov
 Wouter van Ackooy
 Xuecong Liao
+Eli Boyarski
diff --git a/CHANGELOG.rst b/CHANGELOG.rst
index 173347d7b..ffe034332 100644
--- a/CHANGELOG.rst
+++ b/CHANGELOG.rst
@@ -17,17 +17,26 @@
 * Fix ``pytester`` internal plugin to work correctly with latest versions of
   ``zope.interface`` (`#1989`_). Thanks `@nicoddemus`_ for the PR.
 
+* Assert statements of the ``pytester`` plugin again benefit from assertion rewriting (`#1920`_).
+  Thanks `@RonnyPfannschmidt`_ for the report and `@nicoddemus`_ for the PR.
+
 * Specifying tests with colons like ``test_foo.py::test_bar`` for tests in
   subdirectories with ini configuration files now uses the correct ini file
   (`#2148`_).  Thanks `@pelme`_.
 
+* Fail ``testdir.runpytest().assert_outcomes()`` explicitly if the pytest
+  terminal output it relies on is missing. Thanks to `@eli-b`_ for the PR.
+
 *
 
 .. _@lesteve: https://github.com/lesteve
 .. _@malinoff: https://github.com/malinoff
 .. _@pelme: https://github.com/pelme
+.. _@eli-b: https://github.com/eli-b
+
 
 .. _#1989: https://github.com/pytest-dev/pytest/issues/1989
+.. _#1920: https://github.com/pytest-dev/pytest/issues/1920
 .. _#2129: https://github.com/pytest-dev/pytest/issues/2129
 .. _#2148: https://github.com/pytest-dev/pytest/issues/2148
 .. _#2150: https://github.com/pytest-dev/pytest/issues/2150
diff --git a/_pytest/config.py b/_pytest/config.py
index 8578e8aaa..42d1a118a 100644
--- a/_pytest/config.py
+++ b/_pytest/config.py
@@ -421,7 +421,7 @@ class PytestPluginManager(PluginManager):
             importspec = "_pytest." + modname
         else:
             importspec = modname
-        self.rewrite_hook.mark_rewrite(modname)
+        self.rewrite_hook.mark_rewrite(importspec)
         try:
             __import__(importspec)
         except ImportError as e:
diff --git a/_pytest/pytester.py b/_pytest/pytester.py
index b401c4f23..6c63bbbbf 100644
--- a/_pytest/pytester.py
+++ b/_pytest/pytester.py
@@ -367,6 +367,7 @@ class RunResult:
                     for num, cat in outcomes:
                         d[cat] = int(num)
                     return d
+        raise ValueError("Pytest terminal report not found")
 
     def assert_outcomes(self, passed=0, skipped=0, failed=0):
         """ assert that the specified outcomes appear with the respective
diff --git a/testing/test_assertion.py b/testing/test_assertion.py
index c63f26b9c..9115d25e2 100644
--- a/testing/test_assertion.py
+++ b/testing/test_assertion.py
@@ -58,6 +58,23 @@ class TestImportHookInstallation:
             assert 0
         result.stdout.fnmatch_lines([expected])
 
+    def test_rewrite_assertions_pytester_plugin(self, testdir):
+        """
+        Assertions in the pytester plugin must also benefit from assertion
+        rewriting (#1920).
+        """
+        testdir.makepyfile("""
+            pytest_plugins = ['pytester']
+            def test_dummy_failure(testdir):  # how meta!
+                testdir.makepyfile('def test(): assert 0')
+                r = testdir.inline_run()
+                r.assertoutcome(passed=1)
+        """)
+        result = testdir.runpytest_subprocess()
+        result.stdout.fnmatch_lines([
+            '*assert 1 == 0*',
+        ])
+
     @pytest.mark.parametrize('mode', ['plain', 'rewrite'])
     def test_pytest_plugins_rewrite(self, testdir, mode):
         contents = {
diff --git a/testing/test_pytester.py b/testing/test_pytester.py
index 14548808c..49cf43a3e 100644
--- a/testing/test_pytester.py
+++ b/testing/test_pytester.py
@@ -124,3 +124,10 @@ def test_inline_run_clean_modules(testdir):
     test_mod.write("def test_foo(): assert False")
     result2 = testdir.inline_run(str(test_mod))
     assert result2.ret == EXIT_TESTSFAILED
+
+def test_assert_outcomes_after_pytest_erro(testdir):
+    testdir.makepyfile("def test_foo(): assert True")
+
+    result = testdir.runpytest('--unexpected-argument')
+    with pytest.raises(ValueError, message="Pytest terminal report not found"):
+        result.assert_outcomes(passed=0)