diff --git a/HISTORY.rst b/HISTORY.rst
index 9bb538f4..a040ff52 100644
--- a/HISTORY.rst
+++ b/HISTORY.rst
@@ -16,23 +16,27 @@ PlatformIO 2.0
 * Added support for `Microchip PIC32 <http://docs.platformio.org/en/latest/platforms/microchippic32.html>`__
   development platform
   (`issue #438 <https://github.com/platformio/platformio/issues/438>`_)
-* Updated Arduino core for Espressif platform to 2.2.0
-  (`issue #627 <https://github.com/platformio/platformio/issues/627>`_)
 * New boards for `ARM mbed <http://docs.platformio.org/en/latest/frameworks/mbed.html>`__
   framework: ST Nucleo F410RB, ST Nucleo L073RZ and BBC micro:bit
 * Added support for Generic ATTiny boards: ATTiny24, ATTiny25, ATTiny45 and
   ATTiny85
 * Added support for `TI MSP430 <http://docs.platformio.org/en/latest/platforms/timsp430.html>`__
   boards: TI LaunchPad w/ msp430fr4133 and TI LaunchPad w/ msp430fr6989
+* Updated Arduino core for Espressif platform to 2.2.0
+  (`issue #627 <https://github.com/platformio/platformio/issues/627>`_)
+* Updated native SDK for ESP8266 to 1.5
+  (`issue #366 <https://github.com/platformio/platformio/issues/366>`_)
 * PlatformIO Library Registry in JSON format! Implemented
   ``--json-output`` and ``--page`` options for
   `platformio lib search <http://docs.platformio.org/en/latest/userguide/lib/cmd_search.html>`__
   command
   (`issue #604 <https://github.com/platformio/platformio/issues/604>`_)
+* Allowed to unflag(remove) base/initial flags using
+  `build_unflags <http://docs.platformio.org/en/latest/projectconf.html#build-unflags>`__
+  option
+  (`issue #559 <https://github.com/platformio/platformio/issues/559>`_)
 * Allowed multiple VID/PID pairs when detecting serial ports
   (`issue #632 <https://github.com/platformio/platformio/issues/632>`_)
-* Updated native SDK for ESP8266 to 1.5
-  (`issue #366 <https://github.com/platformio/platformio/issues/366>`_)
 * Automatically add ``-DUSB_MANUFACTURER`` with vendor's name
   (`issue #631 <https://github.com/platformio/platformio/issues/631>`_)
 * Automatically reboot Teensy board after upload when Teensy Loader GUI is used
diff --git a/docs/projectconf.rst b/docs/projectconf.rst
index ced07a46..91f2ba23 100644
--- a/docs/projectconf.rst
+++ b/docs/projectconf.rst
@@ -341,6 +341,17 @@ but will be applied only for the project source code from
 This option can be set by global environment variable
 :envvar:`PLATFORMIO_SRC_BUILD_FLAGS`.
 
+``build_unflags``
+^^^^^^^^^^^^^^^^^
+
+Remove base/initial flags which were set by development platform.
+
+.. code-block:: ini
+
+   [env:unflags]
+   build_unflags = -Os -std=gnu++11
+   build_flags = -O2
+
 .. _projectconf_src_filter:
 
 ``src_filter``
diff --git a/platformio/builder/main.py b/platformio/builder/main.py
index ccb4a2d5..69f9e53c 100644
--- a/platformio/builder/main.py
+++ b/platformio/builder/main.py
@@ -42,6 +42,7 @@ commonvars.AddVariables(
     ("FRAMEWORK",),
     ("BUILD_FLAGS",),
     ("SRC_BUILD_FLAGS",),
+    ("BUILD_UNFLAGS",),
     ("SRC_FILTER",),
     ("LIB_DFCYCLIC",),
     ("LIB_IGNORE",),
diff --git a/platformio/builder/tools/platformio.py b/platformio/builder/tools/platformio.py
index 3e51f95b..f897d24a 100644
--- a/platformio/builder/tools/platformio.py
+++ b/platformio/builder/tools/platformio.py
@@ -42,10 +42,14 @@ def BuildProgram(env):
             ASCOM="$ASPPCOM"
         )
 
+    # process extra flags from board
     env.ProcessFlags([
-        env.get("BOARD_OPTIONS", {}).get("build", {}).get("extra_flags"),
-        env.get("BUILD_FLAGS")
+        env.get("BOARD_OPTIONS", {}).get("build", {}).get("extra_flags")
     ])
+    # remove base flags
+    env.ProcessUnFlags(env.get("BUILD_UNFLAGS"))
+    # apply user flags
+    env.ProcessFlags([env.get("BUILD_FLAGS")])
 
     if env.get("FRAMEWORK"):
         env.BuildFrameworks([
@@ -128,6 +132,15 @@ def ProcessFlags(env, flags):
         env.Append(_CPPDEFFLAGS=" %s" % " ".join(undefines))
 
 
+def ProcessUnFlags(env, flags):
+    if not flags:
+        return
+    for var, values in env.ParseFlags(flags).items():
+        for v in values:
+            if v in env[var]:
+                env[var].remove(v)
+
+
 def IsFileWithExt(env, file_, ext):  # pylint: disable=W0613
     if basename(file_).startswith("."):
         return False
@@ -371,6 +384,7 @@ def exists(_):
 def generate(env):
     env.AddMethod(BuildProgram)
     env.AddMethod(ProcessFlags)
+    env.AddMethod(ProcessUnFlags)
     env.AddMethod(IsFileWithExt)
     env.AddMethod(VariantDirWrap)
     env.AddMethod(LookupSources)