diff --git a/HISTORY.rst b/HISTORY.rst
index 7e1722e2..d7fb834a 100644
--- a/HISTORY.rst
+++ b/HISTORY.rst
@@ -20,6 +20,8 @@ PlatformIO 2.0
 2.10.4 (2016-06-??)
 ~~~~~~~~~~~~~~~~~~~
 
+* Better removing unnecessary flags using ``build_unflags`` option
+  (`issue #698 <https://github.com/platformio/platformio/issues/698>`_)
 * Fixed issue with ``platformio init --ide`` command for Python 2.6
 
 2.10.3 (2016-06-15)
diff --git a/docs/frameworks/arduino.rst b/docs/frameworks/arduino.rst
index f7a4877a..db5b6d92 100644
--- a/docs/frameworks/arduino.rst
+++ b/docs/frameworks/arduino.rst
@@ -1211,7 +1211,7 @@ OpenEnergyMonitor
       - RAM
 
     * - ``emonpi``
-      - `emonPi <https://github.com/openenergymonitor/emonpi>`_
+      - `OpenEnergyMonitor emonPi <https://github.com/openenergymonitor/emonpi>`_
       - ATMEGA328P
       - 16 MHz
       - 32 Kb
diff --git a/docs/platforms/atmelavr.rst b/docs/platforms/atmelavr.rst
index 58185e7c..fb181900 100644
--- a/docs/platforms/atmelavr.rst
+++ b/docs/platforms/atmelavr.rst
@@ -826,7 +826,7 @@ OpenEnergyMonitor
       - RAM
 
     * - ``emonpi``
-      - `emonPi <https://github.com/openenergymonitor/emonpi>`_
+      - `OpenEnergyMonitor emonPi <https://github.com/openenergymonitor/emonpi>`_
       - ATMEGA328P
       - 16 MHz
       - 32 Kb
diff --git a/docs/platforms/embedded_boards.rst b/docs/platforms/embedded_boards.rst
index 23721690..bd52ca0c 100644
--- a/docs/platforms/embedded_boards.rst
+++ b/docs/platforms/embedded_boards.rst
@@ -1576,7 +1576,7 @@ OpenEnergyMonitor
       - RAM
 
     * - ``emonpi``
-      - `emonPi <https://github.com/openenergymonitor/emonpi>`_
+      - `OpenEnergyMonitor emonPi <https://github.com/openenergymonitor/emonpi>`_
       - ATMEGA328P
       - 16 MHz
       - 32 Kb
diff --git a/platformio/builder/tools/piomisc.py b/platformio/builder/tools/piomisc.py
index 396ef4b1..6d0095f5 100644
--- a/platformio/builder/tools/piomisc.py
+++ b/platformio/builder/tools/piomisc.py
@@ -122,8 +122,8 @@ def ConvertInoToCpp(env):
             remove(file_)
         except:  # pylint: disable=bare-except
             if isfile(file_):
-                print ("Warning: Could not remove temporary file '%s'. "
-                       "Please remove it manually." % file_)
+                print("Warning: Could not remove temporary file '%s'. "
+                      "Please remove it manually." % file_)
 
     ino_nodes = (env.Glob(join("$PROJECTSRC_DIR", "*.ino")) +
                  env.Glob(join("$PROJECTSRC_DIR", "*.pde")))
@@ -204,9 +204,7 @@ def DumpIDEData(env):
     def get_defines(env_):
         defines = []
         # global symbols
-        for item in env_.get("CPPDEFINES", []):
-            if isinstance(item, list):
-                item = "=".join(item)
+        for item in env.Flatten(env_.get("CPPDEFINES", [])):
             defines.append(env_.subst(item).replace('\\"', '"'))
 
         # special symbol for Atmel AVR MCU
@@ -233,9 +231,7 @@ def DumpIDEData(env):
 
     # https://github.com/platformio/platformio-atom-ide/issues/34
     _new_defines = []
-    for item in env_.get("CPPDEFINES", []):
-        if isinstance(item, list):
-            item = "=".join(item)
+    for item in env.Flatten(env_.get("CPPDEFINES", [])):
         item = item.replace('\\"', '"')
         if " " in item:
             _new_defines.append(item.replace(" ", "\\\\ "))
diff --git a/platformio/builder/tools/platformio.py b/platformio/builder/tools/platformio.py
index 17e3128f..7b866bca 100644
--- a/platformio/builder/tools/platformio.py
+++ b/platformio/builder/tools/platformio.py
@@ -36,12 +36,9 @@ SRC_DEFAULT_FILTER = " ".join([
 def BuildProgram(env):
 
     def _append_pio_macros():
-        if any(["PLATFORMIO=" in str(d) for d in env.get("CPPDEFINES", [])]):
-            return
-        env.Append(
+        env.AppendUnique(
             CPPDEFINES=["PLATFORMIO={0:02d}{1:02d}{2:02d}".format(
-                *pioversion_to_intstr())]
-        )
+                *pioversion_to_intstr())])
 
     _append_pio_macros()
 
@@ -53,12 +50,12 @@ def BuildProgram(env):
         )
 
     # process extra flags from board
-    if "BOARD" in env and "build.extra_flags" in env.BoardConfig():
-        env.ProcessFlags([env.BoardConfig().get("build.extra_flags")])
+    if "BOARD" in env:
+        env.ProcessFlags(env.BoardConfig().get("build.extra_flags"))
     # remove base flags
     env.ProcessUnFlags(env.get("BUILD_UNFLAGS"))
     # apply user flags
-    env.ProcessFlags([env.get("BUILD_FLAGS")])
+    env.ProcessFlags(env.get("BUILD_FLAGS"))
 
     if env.get("FRAMEWORK"):
         env.BuildFrameworks([
@@ -87,7 +84,7 @@ def BuildProgram(env):
         )
 
     # Handle SRC_BUILD_FLAGS
-    env.ProcessFlags([env.get("SRC_BUILD_FLAGS", None)])
+    env.ProcessFlags(env.get("SRC_BUILD_FLAGS"))
 
     env.Append(
         CPPPATH=["$PROJECTSRC_DIR"],
@@ -119,18 +116,17 @@ def BuildProgram(env):
 
 
 def ProcessFlags(env, flags):
-    for f in flags:
-        if not f:
+    if not flags:
+        return
+    parsed_flags = env.ParseFlags(str(flags))
+    for flag in parsed_flags.pop("CPPDEFINES"):
+        if not isinstance(flag, list):
+            env.Append(CPPDEFINES=flag)
             continue
-        parsed_flags = env.ParseFlags(str(f))
-        for flag in parsed_flags.pop("CPPDEFINES"):
-            if not isinstance(flag, list):
-                env.Append(CPPDEFINES=flag)
-                continue
-            if '\"' in flag[1]:
-                flag[1] = flag[1].replace('\"', '\\\"')
-            env.Append(CPPDEFINES=[flag])
-        env.Append(**parsed_flags)
+        if '\"' in flag[1]:
+            flag[1] = flag[1].replace('\"', '\\\"')
+        env.Append(CPPDEFINES=[flag])
+    env.Append(**parsed_flags)
 
     # fix relative CPPPATH & LIBPATH
     for k in ("CPPPATH", "LIBPATH"):
@@ -155,10 +151,17 @@ def ProcessFlags(env, flags):
 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)
+    parsed_flags = env.ParseFlags(flags)
+    all_flags = []
+    for items in parsed_flags.values():
+        all_flags.extend(items)
+    all_flags = set(all_flags)
+
+    for key in parsed_flags.keys():
+        cur_flags = set(env.get(key, []))
+        for item in cur_flags & all_flags:
+            while item in env[key]:
+                env[key].remove(item)
 
 
 def IsFileWithExt(env, file_, ext):  # pylint: disable=W0613