diff --git a/changelog/4592.bugfix.rst b/changelog/4592.bugfix.rst
new file mode 100644
index 000000000..f1eaae7eb
--- /dev/null
+++ b/changelog/4592.bugfix.rst
@@ -0,0 +1 @@
+Fix handling of ``collect_ignore`` via parent ``conftest.py``.
diff --git a/pyproject.toml b/pyproject.toml
index d17b936c1..2a4cd65c1 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -5,6 +5,7 @@ requires = [
   "setuptools-scm",
   "wheel",
 ]
+build-backend = "setuptools.build_meta"
 
 [tool.towncrier]
 package = "pytest"
diff --git a/src/_pytest/main.py b/src/_pytest/main.py
index d0d826bb6..68d5bac40 100644
--- a/src/_pytest/main.py
+++ b/src/_pytest/main.py
@@ -607,6 +607,7 @@ class Session(nodes.FSCollector):
                 yield y
 
     def _collectfile(self, path, handle_dupes=True):
+        assert path.isfile()
         ihook = self.gethookproxy(path)
         if not self.isinitpath(path):
             if ihook.pytest_ignore_collect(path=path, config=self.config):
diff --git a/src/_pytest/python.py b/src/_pytest/python.py
index aaa49f7dd..48962d137 100644
--- a/src/_pytest/python.py
+++ b/src/_pytest/python.py
@@ -599,6 +599,7 @@ class Package(Module):
         return proxy
 
     def _collectfile(self, path, handle_dupes=True):
+        assert path.isfile()
         ihook = self.gethookproxy(path)
         if not self.isinitpath(path):
             if ihook.pytest_ignore_collect(path=path, config=self.config):
@@ -642,11 +643,12 @@ class Package(Module):
             ):
                 continue
 
-            if path.isdir() and path.join("__init__.py").check(file=1):
-                pkg_prefixes.add(path)
-
-            for x in self._collectfile(path):
-                yield x
+            if path.isdir():
+                if path.join("__init__.py").check(file=1):
+                    pkg_prefixes.add(path)
+            else:
+                for x in self._collectfile(path):
+                    yield x
 
 
 def _get_xunit_setup_teardown(holder, attr_name, param_obj=None):
diff --git a/testing/test_collection.py b/testing/test_collection.py
index 36e8a69ce..329182b0f 100644
--- a/testing/test_collection.py
+++ b/testing/test_collection.py
@@ -1144,3 +1144,16 @@ def test_collect_symlink_out_of_tree(testdir):
         ]
     )
     assert result.ret == 0
+
+
+def test_collectignore_via_conftest(testdir, monkeypatch):
+    """collect_ignore in parent conftest skips importing child (issue #4592)."""
+    tests = testdir.mkpydir("tests")
+    tests.ensure("conftest.py").write("collect_ignore = ['ignore_me']")
+
+    ignore_me = tests.mkdir("ignore_me")
+    ignore_me.ensure("__init__.py")
+    ignore_me.ensure("conftest.py").write("assert 0, 'should_not_be_called'")
+
+    result = testdir.runpytest()
+    assert result.ret == EXIT_NOTESTSCOLLECTED
diff --git a/tox.ini b/tox.ini
index f67d06f18..6c216fd71 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,5 +1,6 @@
 [tox]
-minversion = 2.0
+isolated_build = True
+minversion = 3.3
 distshare = {homedir}/.tox/distshare
 # make sure to update environment list in travis.yml and appveyor.yml
 envlist =
@@ -166,7 +167,9 @@ commands =
 
 [testenv:py37-freeze]
 changedir = testing/freeze
+# Disable PEP 517 with pip, which does not work with PyInstaller currently.
 deps =
+    --no-use-pep517
     pyinstaller
 commands =
     {envpython} create_executable.py