diff --git a/tools/export/iar/__init__.py b/tools/export/iar/__init__.py
index 3b60d11e4c..b491f5eed6 100644
--- a/tools/export/iar/__init__.py
+++ b/tools/export/iar/__init__.py
@@ -111,11 +111,9 @@ class IAR(Exporter):
                self.resources.c_sources + self.resources.cpp_sources + \
                self.resources.objects + self.resources.libraries
         flags = self.flags
-        _, macros = self.toolchain.config.get_config_data()
-        defines = ['-D%s' % d for d in macros] if macros else [""]
         c_flags = list(set(flags['common_flags']
-                                    + flags['c_flags']
-                                    + flags['cxx_flags']))
+                           + flags['c_flags']
+                           + flags['cxx_flags']))
         # Flags set in template to be set by user in IDE
         template = ["--vla", "--no_static_destruction"]
         # Flag invalid if set in template
@@ -136,7 +134,6 @@ class IAR(Exporter):
             'device': self.iar_device(),
             'ewp': sep+self.project_name + ".ewp",
             'debugger': debugger,
-            'defines': defines
         }
         ctx.update(flags)
 
diff --git a/tools/export/iar/ewp.tmpl b/tools/export/iar/ewp.tmpl
index 5b769ade6a..cf5b7f0e6e 100644
--- a/tools/export/iar/ewp.tmpl
+++ b/tools/export/iar/ewp.tmpl
@@ -479,9 +479,7 @@
 				</option>
 				<option>
 					<name>ADefines</name>
-					{% for d in defines %}
-					<state>{{d}}</state>
-					{% endfor %}
+					<state></state>
 				</option>
 				<option>
 					<name>AList</name>
diff --git a/tools/toolchains/arm.py b/tools/toolchains/arm.py
index 296ed3896c..1a5e4c976e 100644
--- a/tools/toolchains/arm.py
+++ b/tools/toolchains/arm.py
@@ -147,6 +147,9 @@ class ARM(mbedToolchain):
 
     def get_compile_options(self, defines, includes, for_asm=False):
         opts = ['-D%s' % d for d in defines]
+        config_header = self.get_config_header()
+        if config_header is not None:
+            opts = opts + self.get_config_option(config_header)
         if for_asm:
             return opts
         if self.RESPONSE_FILES:
@@ -154,9 +157,6 @@ class ARM(mbedToolchain):
         else:
             opts += ["-I%s" % i for i in includes]
 
-        config_header = self.get_config_header()
-        if config_header is not None:
-            opts = opts + self.get_config_option(config_header)
         return opts
 
     @hook_tool
diff --git a/tools/toolchains/gcc.py b/tools/toolchains/gcc.py
index 87e3fd219c..cc9760a7d7 100644
--- a/tools/toolchains/gcc.py
+++ b/tools/toolchains/gcc.py
@@ -148,10 +148,9 @@ class GCC(mbedToolchain):
         else:
             opts += ["-I%s" % i for i in includes]
 
-        if not for_asm:
-            config_header = self.get_config_header()
-            if config_header is not None:
-                opts = opts + self.get_config_option(config_header)
+        config_header = self.get_config_header()
+        if config_header is not None:
+            opts = opts + self.get_config_option(config_header)
         return opts
 
     @hook_tool
diff --git a/tools/toolchains/iar.py b/tools/toolchains/iar.py
index 842db05186..40a7e97c83 100644
--- a/tools/toolchains/iar.py
+++ b/tools/toolchains/iar.py
@@ -140,6 +140,9 @@ class IAR(mbedToolchain):
 
     def get_compile_options(self, defines, includes, for_asm=False):
         opts = ['-D%s' % d for d in defines]
+        config_header = self.get_config_header()
+        if config_header is not None:
+            opts = opts + self.get_config_option(config_header)
         if for_asm :
             return opts
         if self.RESPONSE_FILES:
@@ -147,17 +150,12 @@ class IAR(mbedToolchain):
         else:
             opts += ["-I%s" % i for i in includes]
 
-        config_header = self.get_config_header()
-        if config_header is not None:
-            opts = opts + self.get_config_option(config_header)
         return opts
 
     @hook_tool
     def assemble(self, source, object, includes):
-        _, macros = self.config.get_config_data()
-        defines = ['-D%s' % d for d in macros] if macros else [""]
         # Build assemble command
-        cmd = self.asm + self.get_compile_options(self.get_symbols(True), includes, True) + defines + ["-o", object, source]
+        cmd = self.asm + self.get_compile_options(self.get_symbols(True), includes, True) + ["-o", object, source]
 
         # Call cmdline hook
         cmd = self.hook.get_cmdline_assembler(cmd)