diff --git a/mypy/dmypy_server.py b/mypy/dmypy_server.py
index e4e3a56fb774b..54f85f3bfc280 100644
--- a/mypy/dmypy_server.py
+++ b/mypy/dmypy_server.py
@@ -559,13 +559,12 @@ def get_meminfo() -> Dict[str, Any]:
     try:
         import psutil  # type: ignore  # It's not in typeshed yet
     except ImportError:
-        if sys.platform != 'win32':
-            res['memory_psutil_missing'] = (
-                'psutil not found, run pip install mypy[dmypy] '
-                'to install the needed components for dmypy'
-            )
+        res['memory_psutil_missing'] = (
+            'psutil not found, run pip install mypy[dmypy] '
+            'to install the needed components for dmypy'
+        )
     else:
-        process = psutil.Process(os.getpid())
+        process = psutil.Process()
         meminfo = process.memory_info()
         res['memory_rss_mib'] = meminfo.rss / MiB
         res['memory_vms_mib'] = meminfo.vms / MiB
diff --git a/setup.py b/setup.py
index 9c21ebb81edf9..02c02b462197f 100644
--- a/setup.py
+++ b/setup.py
@@ -174,12 +174,10 @@ def run(self):
       classifiers=classifiers,
       cmdclass=cmdclass,
       # When changing this, also update test-requirements.txt.
-      install_requires = ['typed-ast >= 1.3.5, < 1.4.0',
-                          'mypy_extensions >= 0.4.0, < 0.5.0',
-                          ],
+      install_requires=['typed-ast >= 1.3.5, < 1.4.0',
+                        'mypy_extensions >= 0.4.0, < 0.5.0',
+                        ],
       # Same here.
-      extras_require = {
-          'dmypy': 'psutil >= 5.4.0, < 5.5.0; sys_platform!="win32"',
-      },
+      extras_require={'dmypy': 'psutil >= 4.0'},
       include_package_data=True,
       )
diff --git a/test-requirements.txt b/test-requirements.txt
index e7638029850e9..5f310d5930240 100644
--- a/test-requirements.txt
+++ b/test-requirements.txt
@@ -4,7 +4,7 @@ flake8-bugbear; python_version >= '3.5'
 flake8-pyi; python_version >= '3.6'
 lxml==4.2.4
 mypy_extensions>=0.4.0,<0.5.0
-psutil>=5.4.0,<5.5.0; sys_platform!='win32'
+psutil>=4.0
 pytest>=4.4
 pytest-xdist>=1.22
 pytest-cov>=2.4.0