diff --git a/tools/config/__init__.py b/tools/config/__init__.py
index ef76eaf3a7..2b457bd7bc 100644
--- a/tools/config/__init__.py
+++ b/tools/config/__init__.py
@@ -34,6 +34,10 @@ from tools.arm_pack_manager import Cache
 from tools.targets import CUMULATIVE_ATTRIBUTES, TARGET_MAP, \
     generate_py_target, get_resolution_order, Target
 
+try:
+    unicode
+except NameError:
+    unicode = str
 PATH_OVERRIDES = set(["target.bootloader_img"])
 BOOTLOADER_OVERRIDES = set(["target.bootloader_img", "target.restrict_size",
                             "target.mbed_app_start", "target.mbed_app_size"])
diff --git a/tools/toolchains/__init__.py b/tools/toolchains/__init__.py
index a62fe098fc..d248089f37 100644
--- a/tools/toolchains/__init__.py
+++ b/tools/toolchains/__init__.py
@@ -1275,7 +1275,7 @@ class mbedToolchain:
         self.config_file = join(self.build_dir, self.MBED_CONFIG_FILE_NAME)
         # If the file exists, read its current content in prev_data
         if exists(self.config_file):
-            with open(self.config_file, "rt") as f:
+            with open(self.config_file, "r") as f:
                 prev_data = f.read()
         else:
             prev_data = None
@@ -1289,12 +1289,13 @@ class mbedToolchain:
                 self.config_file = None # this means "config file not present"
                 changed = True
             elif crt_data != prev_data: # different content of config file
-                with open(self.config_file, "wt") as f:
+                print("changed!")
+                with open(self.config_file, "w") as f:
                     f.write(crt_data)
                 changed = True
         else: # a previous mbed_config.h does not exist
             if crt_data is not None: # there's configuration data available
-                with open(self.config_file, "wt") as f:
+                with open(self.config_file, "w") as f:
                     f.write(crt_data)
                 changed = True
             else:
@@ -1606,11 +1607,11 @@ from tools.toolchains.gcc import GCC_ARM
 from tools.toolchains.iar import IAR
 
 TOOLCHAIN_CLASSES = {
-    'ARM': ARM_STD,
-    'uARM': ARM_MICRO,
-    'ARMC6': ARMC6,
-    'GCC_ARM': GCC_ARM,
-    'IAR': IAR
+    u'ARM': ARM_STD,
+    u'uARM': ARM_MICRO,
+    u'ARMC6': ARMC6,
+    u'GCC_ARM': GCC_ARM,
+    u'IAR': IAR
 }
 
 TOOLCHAINS = set(TOOLCHAIN_CLASSES.keys())
diff --git a/tools/utils.py b/tools/utils.py
index ebf4ba54a3..e51e5035d9 100644
--- a/tools/utils.py
+++ b/tools/utils.py
@@ -381,6 +381,8 @@ def argparse_type(casedness, prefer_hyphen=False):
             the string, or the hyphens/underscores do not match the expected
             style of the argument.
             """
+            if not isinstance(string, unicode):
+                string = string.decode()
             if prefer_hyphen:
                 newstring = casedness(string).replace("_", "-")
             else:
@@ -399,10 +401,10 @@ def argparse_type(casedness, prefer_hyphen=False):
     return middle
 
 # short cuts for the argparse_type versions
-argparse_uppercase_type = argparse_type(str.upper, False)
-argparse_lowercase_type = argparse_type(str.lower, False)
-argparse_uppercase_hyphen_type = argparse_type(str.upper, True)
-argparse_lowercase_hyphen_type = argparse_type(str.lower, True)
+argparse_uppercase_type = argparse_type(unicode.upper, False)
+argparse_lowercase_type = argparse_type(unicode.lower, False)
+argparse_uppercase_hyphen_type = argparse_type(unicode.upper, True)
+argparse_lowercase_hyphen_type = argparse_type(unicode.lower, True)
 
 def argparse_force_type(case):
     """ validate that an argument passed in (as string) is a member of the list
@@ -412,9 +414,14 @@ def argparse_force_type(case):
         """ The parser type generator"""
         def parse_type(string):
             """ The parser type"""
+            if not isinstance(string, unicode):
+                string = string.decode()
             for option in lst:
-                if case(string) == case(option):
-                    return option
+                try:
+                    if case(string) == case(option):
+                        return option
+                except Exception as e:
+                    print(e)
             raise argparse.ArgumentTypeError(
                 "{0} is not a supported {1}. Supported {1}s are:\n{2}".
                 format(string, type_name, columnate(lst)))
@@ -422,8 +429,8 @@ def argparse_force_type(case):
     return middle
 
 # these two types convert the case of their arguments _before_ validation
-argparse_force_uppercase_type = argparse_force_type(str.upper)
-argparse_force_lowercase_type = argparse_force_type(str.lower)
+argparse_force_uppercase_type = argparse_force_type(unicode.upper)
+argparse_force_lowercase_type = argparse_force_type(unicode.lower)
 
 def argparse_many(func):
     """ An argument parser combinator that takes in an argument parser and