diff --git a/patroni/ha.py b/patroni/ha.py
index 7ed1e139..fdc2ce07 100644
--- a/patroni/ha.py
+++ b/patroni/ha.py
@@ -1290,7 +1290,8 @@ class Ha(object):
                 data_sysid = self.state_handler.sysid
                 if not self.sysid_valid(data_sysid):
                     # data directory is not empty, but no valid sysid, cluster must be broken, suggest reinit
-                    return "data dir for the cluster is not empty, but system ID is invalid; consider doing reinitalize"
+                    return ("data dir for the cluster is not empty, but system ID is invalid; consider doing"
+                            "reinitialize")
 
                 if self.sysid_valid(self.cluster.initialize):
                     if self.cluster.initialize != data_sysid:
diff --git a/patroni/postgresql/__init__.py b/patroni/postgresql/__init__.py
index 5c0ad8cc..7fba00d3 100644
--- a/patroni/postgresql/__init__.py
+++ b/patroni/postgresql/__init__.py
@@ -516,7 +516,7 @@ class Postgresql(object):
             self.set_state('stopping')
 
         # Send signal to postmaster to stop
-        success = postmaster.signal_stop(mode)
+        success = postmaster.signal_stop(mode, self.pgcommand('pg_ctl'))
         if success is not None:
             if success and on_safepoint:
                 on_safepoint()
@@ -533,11 +533,10 @@ class Postgresql(object):
 
         return True, True
 
-    @staticmethod
-    def terminate_starting_postmaster(postmaster):
+    def terminate_starting_postmaster(self, postmaster):
         """Terminates a postmaster that has not yet opened ports or possibly even written a pid file. Blocks
         until the process goes away."""
-        postmaster.signal_stop('immediate')
+        postmaster.signal_stop('immediate', self.pgcommand('pg_ctl'))
         postmaster.wait()
 
     def _wait_for_connection_close(self, postmaster):
diff --git a/patroni/postgresql/postmaster.py b/patroni/postgresql/postmaster.py
index f2f23b25..add11488 100644
--- a/patroni/postgresql/postmaster.py
+++ b/patroni/postgresql/postmaster.py
@@ -22,7 +22,7 @@ logger = logging.getLogger(__name__)
 STOP_SIGNALS = {
     'smart': signal.SIGTERM,
     'fast': signal.SIGINT,
-    'immediate': signal.SIGQUIT if os.name != 'nt' else signal.SIGABRT,
+    'immediate': signal.SIGQUIT,
 }
 
 
@@ -105,7 +105,7 @@ class PostmasterProcess(psutil.Process):
         except psutil.NoSuchProcess:
             return None
 
-    def signal_stop(self, mode):
+    def signal_stop(self, mode, pg_ctl='pg_ctl'):
         """Signal postmaster process to stop
 
         :returns None if signaled, True if process is already gone, False if error
@@ -113,6 +113,8 @@ class PostmasterProcess(psutil.Process):
         if self.is_single_user:
             logger.warning("Cannot stop server; single-user server is running (PID: {0})".format(self.pid))
             return False
+        if os.name != 'posix':
+            return self.pg_ctl_kill(mode, pg_ctl)
         try:
             self.send_signal(STOP_SIGNALS[mode])
         except psutil.NoSuchProcess:
@@ -123,6 +125,17 @@ class PostmasterProcess(psutil.Process):
 
         return None
 
+    def pg_ctl_kill(self, mode, pg_ctl):
+        SIGNALNAME = {"smart": "TERM", "fast": "INT", "immediate": "QUIT"}[mode]
+        try:
+            status = subprocess.call([pg_ctl, "kill", SIGNALNAME, str(self.pid)])
+        except OSError:
+            return False
+        if status == 0:
+            return None
+        else:
+            return not self.is_running()
+
     def wait_for_user_backends_to_close(self):
         # These regexps are cross checked against versions PostgreSQL 9.1 .. 11
         aux_proc_re = re.compile("(?:postgres:)( .*:)? (?:(?:archiver|startup|autovacuum launcher|autovacuum worker|"
diff --git a/tests/test_postmaster.py b/tests/test_postmaster.py
index 83afaeea..a62436e3 100644
--- a/tests/test_postmaster.py
+++ b/tests/test_postmaster.py
@@ -76,6 +76,21 @@ class TestPostmasterProcess(unittest.TestCase):
         self.assertEqual(proc.signal_stop('immediate'), True)
         self.assertEqual(proc.signal_stop('immediate'), False)
 
+    @patch('psutil.Process.__init__', Mock())
+    @patch('patroni.postgresql.postmaster.os')
+    @patch('subprocess.call', Mock(side_effect=[0, OSError, 1]))
+    @patch('psutil.Process.pid', Mock(return_value=123))
+    @patch('psutil.Process.is_running', Mock(return_value=False))
+    def test_signal_stop_nt(self, mock_os):
+        mock_os.configure_mock(name="nt")
+        proc = PostmasterProcess(-123)
+        self.assertEqual(proc.signal_stop('immediate'), False)
+
+        proc = PostmasterProcess(123)
+        self.assertEqual(proc.signal_stop('immediate'), None)
+        self.assertEqual(proc.signal_stop('immediate'), False)
+        self.assertEqual(proc.signal_stop('immediate'), True)
+
     @patch('psutil.Process.__init__', Mock())
     @patch('psutil.wait_procs')
     def test_wait_for_user_backends_to_close(self, mock_wait):