diff --git a/HISTORY.rst b/HISTORY.rst
index b5f837ab..9f8561b6 100644
--- a/HISTORY.rst
+++ b/HISTORY.rst
@@ -7,6 +7,9 @@ PlatformIO 2.0
 2.3.6 (2015-??-??)
 ~~~~~~~~~~~~~~~~~~
 
+* Fixed ESP-12E flash size
+  (`pull #333 <https://github.com/platformio/platformio/pull/333>`_)
+
 2.3.5 (2015-11-18)
 ~~~~~~~~~~~~~~~~~~
 
diff --git a/platformio/builder/scripts/espressif.py b/platformio/builder/scripts/espressif.py
index fde0f7b6..2496111c 100644
--- a/platformio/builder/scripts/espressif.py
+++ b/platformio/builder/scripts/espressif.py
@@ -103,6 +103,8 @@ if "FRAMEWORK" in env:
         ]
     )
 
+_board_max_rom = int(
+    env.get("BOARD_OPTIONS", {}).get("upload", {}).get("maximum_size", 0))
 env.Append(
     BUILDERS=dict(
         ElfToBin=Builder(
@@ -113,8 +115,9 @@ env.Append(
                 "-bo", "$TARGET",
                 "-bm", "dio",
                 "-bf", "${BOARD_OPTIONS['build']['f_cpu'][:2]}",
-                "-bz", str(int(env.get("BOARD_OPTIONS", {}).get(
-                    "upload", {}).get("maximum_size") / 1024)) + "K",
+                "-bz",
+                "%dK" % (_board_max_rom / 1024) if _board_max_rom < 1048576
+                else "%dM" % (_board_max_rom / 1048576),
                 "-bs", ".text",
                 "-bp", "4096",
                 "-ec",