diff --git a/source/CMakeLists.txt b/source/CMakeLists.txt
index f98a2ec9..0932efb1 100755
--- a/source/CMakeLists.txt
+++ b/source/CMakeLists.txt
@@ -86,17 +86,15 @@ if (YOTTA_CFG_MICROBIT_CONFIGFILE)
 endif ()
 
 if(CMAKE_COMPILER_IS_GNUCC)
-  file(REMOVE "asm/CortexContextSwitch.s")
-  configure_file("asm/CortexContextSwitch.s.gcc" "asm/CortexContextSwitch.s" COPYONLY)
+  set(YOTTA_AUTO_MICROBIT-DAL_S_FILES
+    "asm/TOOLCHAIN_GCC_ARM/CortexContextSwitch.s"
+  )
 else()
-  file(REMOVE "asm/CortexContextSwitch.s")
-  configure_file("asm/CortexContextSwitch.s.armcc" "asm/CortexContextSwitch.s" COPYONLY)
+  set(YOTTA_AUTO_MICROBIT-DAL_S_FILES
+    "asm/TOOLCHAIN_ARM_STD/CortexContextSwitch.S"
+  )
 endif()
 
-set(YOTTA_AUTO_MICROBIT-DAL_S_FILES
-    "asm/CortexContextSwitch.s"
-)
-
 add_library(microbit-dal
     ${YOTTA_AUTO_MICROBIT-DAL_CPP_FILES}
     ${YOTTA_AUTO_MICROBIT-DAL_S_FILES}
diff --git a/source/asm/CortexContextSwitch.s.armcc b/source/asm/TOOLCHAIN_ARM_STD/CortexContextSwitch.S
similarity index 100%
rename from source/asm/CortexContextSwitch.s.armcc
rename to source/asm/TOOLCHAIN_ARM_STD/CortexContextSwitch.S
diff --git a/source/asm/CortexContextSwitch.s.gcc b/source/asm/TOOLCHAIN_GCC_ARM/CortexContextSwitch.s
similarity index 100%
rename from source/asm/CortexContextSwitch.s.gcc
rename to source/asm/TOOLCHAIN_GCC_ARM/CortexContextSwitch.s