diff --git a/HISTORY.rst b/HISTORY.rst
index 1089d25d..9801729e 100644
--- a/HISTORY.rst
+++ b/HISTORY.rst
@@ -8,6 +8,11 @@ PlatformIO Core 5
 
 **A professional collaborative platform for embedded development**
 
+5.2.3 (2021-??-??)
+~~~~~~~~~~~~~~~~~~
+
+- Fixed an issue when the "$PROJECT_DIR" gets the full path to "platformio.ini", not the directory name (`issue #4086 <https://github.com/platformio/platformio-core/issues/4086>`_)
+
 5.2.2 (2021-10-20)
 ~~~~~~~~~~~~~~~~~~
 
diff --git a/platformio/debug/config/base.py b/platformio/debug/config/base.py
index 65ceba60..de726bc9 100644
--- a/platformio/debug/config/base.py
+++ b/platformio/debug/config/base.py
@@ -210,7 +210,7 @@ class DebugConfigBase:  # pylint: disable=too-many-instance-attributes
         patterns = {
             "PLATFORMIO_CORE_DIR": get_project_core_dir(),
             "PYTHONEXE": proc.get_pythonexe_path(),
-            "PROJECT_DIR": self.project_config.path,
+            "PROJECT_DIR": os.getcwd(),
             "PROG_PATH": program_path,
             "PROG_DIR": os.path.dirname(program_path),
             "PROG_NAME": os.path.basename(os.path.splitext(program_path)[0]),