diff --git a/CMakeLists.txt b/CMakeLists.txt
index 8ba477b03..ab1a3834d 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -10,7 +10,7 @@
 # @TAG(DATA61_GPL)
 #
 
-cmake_minimum_required(VERSION 3.7.2)
+cmake_minimum_required(VERSION 3.8.2)
 include(CheckCCompilerFlag)
 project(seL4 C ASM)
 
@@ -354,16 +354,17 @@ set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -T ${linker_lds_path}")
 # Need a custom build command as we need to not have our already pre-processed file get
 # processed again, which means either using a .ii file or explicitly saying -x cpp-output.
 # Unfortunately  and cmake doesn't understand .ii files directly so we do the latter approach
+separate_arguments(args NATIVE_COMMAND "${custom_command_c_flags} ${CMAKE_C_FLAGS}")
 add_custom_command(OUTPUT kernel_all.o
     # Take the opportunity to check for circular includes
     COMMAND ${CIRCULAR_INCLUDES} < kernel_all_pp.c
-    COMMAND echo "${custom_command_c_flags}" "${CMAKE_C_FLAGS}" -x cpp-output kernel_all_pp.c |
-        xargs ${ccache} ${CMAKE_C_COMPILER} -ffreestanding -c -o kernel_all.o
+    COMMAND ${ccache} ${CMAKE_C_COMPILER} -ffreestanding -c -o kernel_all.o "${args}" -x cpp-output kernel_all_pp.c
     # Cannot make the kernel.elf executable properly depend upon the linker script so depend upon it
     # here
     DEPENDS kernel_all_pp.c kernel_all_pp_wrapper ${c_arguments_deps} linker_ld_wrapper "${linker_lds_path}"
     VERBATIM
     COMMENT "Compiling concatenated kernel sources"
+    COMMAND_EXPAND_LISTS
 )
 
 add_custom_target(kernel_all_wrapper
diff --git a/tools/helpers.cmake b/tools/helpers.cmake
index 05fb4c340..e2abf63c5 100644
--- a/tools/helpers.cmake
+++ b/tools/helpers.cmake
@@ -10,7 +10,7 @@
 # @TAG(DATA61_GPL)
 #
 
-cmake_minimum_required(VERSION 3.7.2)
+cmake_minimum_required(VERSION 3.8.2)
 
 include(CMakeDependentOption)
 
@@ -56,19 +56,18 @@ function(GenCPPCommand output input)
     get_filename_component(output_absolute "${output}" ABSOLUTE BASE_DIR "${CMAKE_CURRENT_BINARY_DIR}")
     get_absolute_source_or_binary(input_absolute "${input}")
     file(RELATIVE_PATH rel_target_path "${CMAKE_BINARY_DIR}" "${output_absolute}")
+    # The flags are stored as regular space separated command line. As we use COMMAND_EXPAND_LISTS
+    # in the COMMAND we need to first turn our arguments into a proper list for re-expansion
+    separate_arguments(args NATIVE_COMMAND "${CPP_EXTRA_FLAGS} ${CMAKE_C_FLAGS}")
     add_custom_command(OUTPUT "${output_absolute}" OUTPUT "${output_absolute}.d"
-        # Pipe are arguments through sed to turn lists from generator expressions into
-        # proper space separated argument lists. Note that lists from generator expressions
-        # will *not* be separated by the separate_arguments cmake command since separate_arguments
-        # is invoke during generation, not during building and hence generator expressions will
-        # not yet be filled in
-        COMMAND echo "${CPP_EXTRA_FLAGS}" "${CMAKE_C_FLAGS}" -x c ${input_absolute}
-            | xargs "${CMAKE_C_COMPILER}" -MMD -MT "${rel_target_path}"
-                -MF "${output_absolute}.d" -E -o "${output_absolute}"
+        COMMAND "${CMAKE_C_COMPILER}" -MMD -MT "${rel_target_path}"
+                -MF "${output_absolute}.d" -E -o "${output_absolute}" "${args}"
+                -x c "${input_absolute}"
         DEPENDS "${input_absolute}" ${CPP_EXTRA_DEPS}
         COMMENT "Preprocessing ${input} into ${output}"
         DEPFILE "${output_absolute}.d"
         VERBATIM
+        COMMAND_EXPAND_LISTS
     )
     if(NOT "${CPP_TARGET}" STREQUAL "")
         add_custom_target(${CPP_TARGET}