diff --git a/platformio/project/config.py b/platformio/project/config.py
index 8e4ec096..7f2efb03 100644
--- a/platformio/project/config.py
+++ b/platformio/project/config.py
@@ -276,6 +276,8 @@ class ProjectConfigBase(object):
 
         if value == MISSING:
             value = default if default != MISSING else option_meta.default
+        if callable(value):
+            value = value()
         if value == MISSING:
             return None
 
diff --git a/platformio/project/options.py b/platformio/project/options.py
index c12679b9..ee5fd603 100644
--- a/platformio/project/options.py
+++ b/platformio/project/options.py
@@ -60,7 +60,7 @@ class ConfigOption(object):  # pylint: disable=too-many-instance-attributes
             type="string",
             multiple=self.multiple,
             sysenvvar=self.sysenvvar,
-            default=self.default,
+            default=self.default() if callable(self.default) else self.default,
         )
         if isinstance(self.type, click.ParamType):
             result["type"] = self.type.name
@@ -168,7 +168,7 @@ ProjectOptions = OrderedDict(
                 ),
                 oldnames=["home_dir"],
                 sysenvvar="PLATFORMIO_CORE_DIR",
-                default=get_default_core_dir(),
+                default=get_default_core_dir,
                 validate=validate_dir,
             ),
             ConfigPlatformioOption(
diff --git a/tests/test_projectconf.py b/tests/test_projectconf.py
index b3e85863..0fada8c3 100644
--- a/tests/test_projectconf.py
+++ b/tests/test_projectconf.py
@@ -254,9 +254,15 @@ def test_sysenv_options(config):
     os.environ["PLATFORMIO_HOME_DIR"] = custom_core_dir
     os.environ["PLATFORMIO_SRC_DIR"] = custom_src_dir
     os.environ["PLATFORMIO_BUILD_DIR"] = custom_build_dir
-    assert config.get("platformio", "core_dir") == os.path.realpath(custom_core_dir)
-    assert config.get("platformio", "src_dir") == os.path.realpath(custom_src_dir)
-    assert config.get("platformio", "build_dir") == os.path.realpath(custom_build_dir)
+    assert os.path.realpath(config.get("platformio", "core_dir")) == os.path.realpath(
+        custom_core_dir
+    )
+    assert os.path.realpath(config.get("platformio", "src_dir")) == os.path.realpath(
+        custom_src_dir
+    )
+    assert os.path.realpath(config.get("platformio", "build_dir")) == os.path.realpath(
+        custom_build_dir
+    )
 
     # cleanup system environment variables
     del os.environ["PLATFORMIO_BUILD_FLAGS"]