diff --git a/HISTORY.rst b/HISTORY.rst
index dfae91a9..9897b738 100644
--- a/HISTORY.rst
+++ b/HISTORY.rst
@@ -11,6 +11,7 @@ PlatformIO 4.0
 
 * Update SCons tool to 3.1.1
 * Remove ProjectConfig cache when "platformio.ini" was modified outside
+* Fixed an issue with PIO Unified Debugger on Windows OS when debug server is piped
 
 4.0.2 (2019-08-23)
 ~~~~~~~~~~~~~~~~~~
diff --git a/platformio/commands/debug/helpers.py b/platformio/commands/debug/helpers.py
index 91f06318..33e1e855 100644
--- a/platformio/commands/debug/helpers.py
+++ b/platformio/commands/debug/helpers.py
@@ -19,7 +19,7 @@ from hashlib import sha1
 from io import BytesIO
 from os.path import isfile
 
-from platformio import exception, util
+from platformio import exception, fs, util
 from platformio.commands.platform import \
     platform_install as cmd_platform_install
 from platformio.commands.run import cli as cmd_run
@@ -165,11 +165,11 @@ def configure_esp32_load_cmds(debug_options, configuration):
 
     mon_cmds = [
         'monitor program_esp32 "{{{path}}}" {offset} verify'.format(
-            path=item['path'], offset=item['offset'])
+            path=fs.to_unix_path(item['path']), offset=item['offset'])
         for item in configuration.get("flash_extra_images")
     ]
     mon_cmds.append('monitor program_esp32 "{%s.bin}" 0x10000 verify' %
-                    configuration['prog_path'][:-4])
+                    fs.to_unix_path(configuration['prog_path'][:-4]))
     return mon_cmds
 
 
diff --git a/platformio/commands/debug/process.py b/platformio/commands/debug/process.py
index f363ccb5..87ad74ec 100644
--- a/platformio/commands/debug/process.py
+++ b/platformio/commands/debug/process.py
@@ -17,6 +17,7 @@ import signal
 import click
 from twisted.internet import protocol  # pylint: disable=import-error
 
+from platformio import fs
 from platformio.compat import string_types
 from platformio.proc import get_pythonexe_path
 from platformio.project.helpers import get_project_core_dir
@@ -38,6 +39,11 @@ class BaseProcess(protocol.ProcessProtocol, object):
         _patterns = self.COMMON_PATTERNS.copy()
         _patterns.update(patterns or {})
 
+        for key, value in _patterns.items():
+            if key.endswith(("_DIR", "_PATH")):
+                print(13, key)
+                _patterns[key] = fs.to_unix_path(value)
+
         def _replace(text):
             for key, value in _patterns.items():
                 pattern = "$%s" % key
diff --git a/platformio/commands/debug/server.py b/platformio/commands/debug/server.py
index 98f1e0e1..e5bc6e45 100644
--- a/platformio/commands/debug/server.py
+++ b/platformio/commands/debug/server.py
@@ -18,7 +18,7 @@ from os.path import isdir, isfile, join
 from twisted.internet import error  # pylint: disable=import-error
 from twisted.internet import reactor  # pylint: disable=import-error
 
-from platformio import exception, util
+from platformio import exception, fs, util
 from platformio.commands.debug.process import BaseProcess
 from platformio.proc import where_is_program
 
@@ -74,7 +74,7 @@ class DebugServer(BaseProcess):
             str_args = " ".join(
                 [arg if arg.startswith("-") else '"%s"' % arg for arg in args])
             self._debug_port = '| "%s" %s' % (server_executable, str_args)
-            self._debug_port = self._debug_port.replace("\\", "\\\\")
+            self._debug_port = fs.to_unix_path(self._debug_port)
         else:
             env = os.environ.copy()
             # prepend server "lib" folder to LD path