diff --git a/src/_pytest/config/__init__.py b/src/_pytest/config/__init__.py
index 3140e1c0f..6a8ac84ce 100644
--- a/src/_pytest/config/__init__.py
+++ b/src/_pytest/config/__init__.py
@@ -153,6 +153,7 @@ def main(
     :returns: An exit code.
     """
     try:
+        old_pytest_version = os.environ.get("PYTEST_VERSION")
         os.environ["PYTEST_VERSION"] = __version__
         try:
             config = _prepareconfig(args, plugins)
@@ -189,7 +190,10 @@ def main(
             tw.line(f"ERROR: {msg}\n", red=True)
         return ExitCode.USAGE_ERROR
     finally:
-        os.environ.pop("PYTEST_VERSION", None)
+        if old_pytest_version is None:
+            os.environ.pop("PYTEST_VERSION", None)
+        else:
+            os.environ["PYTEST_VERSION"] = old_pytest_version               
 
 
 def console_main() -> int:
diff --git a/testing/test_runner.py b/testing/test_runner.py
index c4fb85a7e..d3ddc5d9a 100644
--- a/testing/test_runner.py
+++ b/testing/test_runner.py
@@ -1097,6 +1097,7 @@ def test_outcome_exception_bad_msg() -> None:
 
 
 def test_pytest_version_env_var(pytester: Pytester, monkeypatch: MonkeyPatch) -> None:
+    os.environ["PYTEST_VERSION"] = "old version"
     pytester.makepyfile(
         """
         import pytest
@@ -1109,4 +1110,4 @@ def test_pytest_version_env_var(pytester: Pytester, monkeypatch: MonkeyPatch) ->
     )
     result = pytester.runpytest_inprocess()
     assert result.ret == ExitCode.OK
-    assert "PYTEST_VERSION" not in os.environ
+    assert os.environ["PYTEST_VERSION"] == "old version"