diff --git a/platformio/builder/scripts/basearm.py b/platformio/builder/scripts/basearm.py
index 94ccfec4..0cb81b83 100644
--- a/platformio/builder/scripts/basearm.py
+++ b/platformio/builder/scripts/basearm.py
@@ -11,18 +11,17 @@ env = DefaultEnvironment()
 
 env.Replace(
     AR="arm-none-eabi-ar",
-    AS="arm-none-eabi-gcc",
+    AS="arm-none-eabi-as",
     CC="arm-none-eabi-gcc",
     CXX="arm-none-eabi-g++",
     OBJCOPY="arm-none-eabi-objcopy",
     RANLIB="arm-none-eabi-ranlib",
     SIZETOOL="arm-none-eabi-size",
 
-    ASCOM=("$AS -o $TARGET -c -x assembler-with-cpp "
-           "$CFLAGS $CCFLAGS $_CCCOMCOM $SOURCES"),
-
     ARFLAGS=["rcs"],
 
+    ASPPFLAGS=["-x", "assembler-with-cpp"],
+
     CPPFLAGS=[
         "-g",   # include debugging info (so errors include line numbers)
         "-Os",  # optimize for size
@@ -58,8 +57,7 @@ if env.get("BOARD_OPTIONS", {}).get("build", {}).get("cpu", "")[-2:] == "m4":
     env.Append(
         ASFLAGS=[
             "-mfloat-abi=hard",
-            "-mfpu=fpv4-sp-d16",
-            "-fsingle-precision-constant"
+            "-mfpu=fpv4-sp-d16"
         ],
         CCFLAGS=[
             "-mfloat-abi=hard",
diff --git a/platformio/builder/scripts/baseavr.py b/platformio/builder/scripts/baseavr.py
index f089937b..912250bf 100644
--- a/platformio/builder/scripts/baseavr.py
+++ b/platformio/builder/scripts/baseavr.py
@@ -11,19 +11,18 @@ env = DefaultEnvironment()
 
 env.Replace(
     AR="avr-ar",
-    AS="avr-gcc",
+    AS="avr-as",
     CC="avr-gcc",
     CXX="avr-g++",
     OBJCOPY="avr-objcopy",
     RANLIB="avr-ranlib",
     SIZETOOL="avr-size",
 
-    ASCOM=("$AS -o $TARGET -c -x assembler-with-cpp "
-           "$CFLAGS $CCFLAGS $_CCCOMCOM $SOURCES"),
-
     ARFLAGS=["rcs"],
 
-    CCFLAGS=[
+    ASPPFLAGS=["-x", "assembler-with-cpp"],
+
+    CPPFLAGS=[
         "-g",  # include debugging info (so errors include line numbers)
         "-Os",  # optimize for size
         "-Wall",  # show warnings
@@ -33,15 +32,15 @@ env.Replace(
         "-mmcu=$BOARD_MCU"
     ],
 
+    CPPDEFINES=[
+        "F_CPU=$BOARD_F_CPU"
+    ],
+
     CXXFLAGS=[
         "-fno-exceptions",
         "-fno-threadsafe-statics"
     ],
 
-    CPPDEFINES=[
-        "F_CPU=$BOARD_F_CPU"
-    ],
-
     LINKFLAGS=[
         "-Os",
         "-mmcu=$BOARD_MCU",
diff --git a/platformio/builder/scripts/timsp430.py b/platformio/builder/scripts/timsp430.py
index 38acec2f..98fbd1d1 100644
--- a/platformio/builder/scripts/timsp430.py
+++ b/platformio/builder/scripts/timsp430.py
@@ -16,18 +16,17 @@ env = DefaultEnvironment()
 
 env.Replace(
     AR="msp430-ar",
-    AS="msp430-gcc",
+    AS="msp430-as",
     CC="msp430-gcc",
     CXX="msp430-g++",
     OBJCOPY="msp430-objcopy",
     RANLIB="msp430-ranlib",
     SIZETOOL="msp430-size",
 
-    ASCOM=("$AS -o $TARGET -c -x assembler-with-cpp "
-           "$CFLAGS $CCFLAGS $_CCCOMCOM $SOURCES"),
-
     ARFLAGS=["rcs"],
 
+    ASPPFLAGS=["-x", "assembler-with-cpp"],
+
     CCFLAGS=[
         "-g",  # include debugging info (so errors include line numbers)
         "-Os",  # optimize for size
diff --git a/platformio/builder/tools/platformio.py b/platformio/builder/tools/platformio.py
index 153966ff..79dd62a6 100644
--- a/platformio/builder/tools/platformio.py
+++ b/platformio/builder/tools/platformio.py
@@ -9,12 +9,20 @@ from os.path import basename, dirname, isdir, isfile, join, normpath
 from time import sleep
 
 from SCons.Script import Exit, SConscript, SConscriptChdir
+from SCons.Util import case_sensitive_suffixes
 from serial import Serial
 
 from platformio.util import get_serialports
 
 
 def ProcessGeneral(env):
+    # fix ASM handling under non-casitive OS
+    if not case_sensitive_suffixes('.s', '.S'):
+        env.Replace(
+            AS="$CC",
+            ASCOM="$ASPPCOM"
+        )
+
     if "extra_flags" in env.get("BOARD_OPTIONS", {}).get("build", {}):
         env.MergeFlags(env.subst("${BOARD_OPTIONS['build']['extra_flags']}"))