diff --git a/HISTORY.rst b/HISTORY.rst
index 2b13a6e4..119c651f 100644
--- a/HISTORY.rst
+++ b/HISTORY.rst
@@ -34,6 +34,8 @@ PlatformIO 3.0
 * Use C++11 by default for CLion IDE based projects
   (`pull #873 <https://github.com/platformio/platformio-core/pull/873>`_)
 * Escape project path when Glob matching is used
+* Do not overwrite project configuration variables when system environment
+  variables are set
 * Fixed package installing with VCS branch for Python 2.7.3
   (`issue #885 <https://github.com/platformio/platformio-core/issues/885>`_)
 
@@ -68,7 +70,7 @@ PlatformIO 3.0
 
 * Development platform `Linux ARM <https://github.com/platformio/platform-linux_arm>`__
 
-  + Added support for Samsung ARTIK boards (520, 710, 1020) and ARTIK SDK
+  + Added support for Samsung ARTIK boards (520, 530, 710, 1020) and ARTIK SDK
     (`issue #353 <https://github.com/platformio/platformio-core/issues/353>`_)
 
 * Development platform `Nordic nRF51 <https://github.com/platformio/platform-nordicnrf51>`__
diff --git a/platformio/__init__.py b/platformio/__init__.py
index 5692677f..847dc6e1 100644
--- a/platformio/__init__.py
+++ b/platformio/__init__.py
@@ -14,7 +14,7 @@
 
 import sys
 
-VERSION = (3, 3, "0a10")
+VERSION = (3, 3, "0a11")
 __version__ = ".".join([str(s) for s in VERSION])
 
 __title__ = "platformio"
diff --git a/platformio/builder/main.py b/platformio/builder/main.py
index 13201f48..5fbc2174 100644
--- a/platformio/builder/main.py
+++ b/platformio/builder/main.py
@@ -117,8 +117,13 @@ elif not int(ARGUMENTS.get("PIOVERBOSE", 0)):
 for var in ("BUILD_FLAGS", "SRC_BUILD_FLAGS", "SRC_FILTER", "EXTRA_SCRIPT",
             "UPLOAD_PORT", "UPLOAD_FLAGS", "LIB_EXTRA_DIRS"):
     k = "PLATFORMIO_%s" % var
-    if environ.get(k):
+    if k not in environ:
+        continue
+    if var in ("UPLOAD_PORT", "EXTRA_SCRIPT") or not env.get(var):
         env[var] = environ.get(k)
+    else:
+        env[var] = "%s%s%s" % (environ.get(k), ", "
+                               if var == "LIB_EXTRA_DIRS" else " ", env[var])
 
 # Parse comma separated items
 for opt in ("PIOFRAMEWORK", "LIB_DEPS", "LIB_IGNORE", "LIB_EXTRA_DIRS"):