diff --git a/src/arch/xtensa/CMakeLists.txt b/src/arch/xtensa/CMakeLists.txt
index a10ace5ee..80e3074b8 100644
--- a/src/arch/xtensa/CMakeLists.txt
+++ b/src/arch/xtensa/CMakeLists.txt
@@ -22,6 +22,8 @@ elseif(CONFIG_MT8188)
         set(platform_folder mt8188)
 elseif(CONFIG_MT8195)
 	set(platform_folder mt8195)
+else()
+	message(FATAL_ERROR "Platform not defined, check your Kconfiguration?")
 endif()
 
 set(fw_name ${CONFIG_RIMAGE_SIGNING_SCHEMA})
diff --git a/src/platform/Kconfig b/src/platform/Kconfig
index d1c13c88a..9ee45422b 100644
--- a/src/platform/Kconfig
+++ b/src/platform/Kconfig
@@ -5,7 +5,9 @@ menu "Platform"
 choice
 	prompt "Platform"
 	default ZEPHYR_POSIX if ARCH_POSIX
-	default TIGERLAKE
+	# It's not really 'optional' but no value is much less confusing
+	# than falling back on a totally random value.
+	optional
 
 config TIGERLAKE
 	bool "Build for Tigerlake"
diff --git a/zephyr/CMakeLists.txt b/zephyr/CMakeLists.txt
index 9ca5c053a..9d92a67db 100644
--- a/zephyr/CMakeLists.txt
+++ b/zephyr/CMakeLists.txt
@@ -363,6 +363,9 @@ zephyr_library_sources_ifdef(CONFIG_LIBRARY
 	${SOF_DRIVERS_PATH}/host/ipc.c
 )
 
+if(NOT DEFINED PLATFORM)
+	message(FATAL_ERROR "PLATFORM is not defined, check your Kconfiguration?")
+endif()
 zephyr_include_directories(${SOF_PLATFORM_PATH}/${PLATFORM}/include)
 
 # Mandatory Files used on all platforms.