diff --git a/cmake/options.cmake b/cmake/options.cmake
index 1c77653..1a7e6db 100644
--- a/cmake/options.cmake
+++ b/cmake/options.cmake
@@ -32,14 +32,6 @@ message ("-- Host:    ${_host}")
 set (_target "${CMAKE_SYSTEM_NAME}/${CMAKE_SYSTEM_PROCESSOR}")
 message ("-- Target:  ${_target}")
 
-if (NOT DEFINED MACHINE)
-  set (MACHINE "Generic")
-endif (NOT DEFINED MACHINE)
-message ("-- Machine: ${MACHINE}")
-
-# handle if '-' in machine name
-string (REPLACE "-" "_" MACHINE ${MACHINE})
-
 if (NOT DEFINED PROJECT_SYSTEM)
   string (TOLOWER ${CMAKE_SYSTEM_NAME}      PROJECT_SYSTEM)
   string (TOUPPER ${CMAKE_SYSTEM_NAME}      PROJECT_SYSTEM_UPPER)
@@ -50,8 +42,14 @@ if("${PROJECT_PROCESSOR}" STREQUAL "arm64")
   set (PROJECT_PROCESSOR "aarch64")
 endif()
 string (TOUPPER ${PROJECT_PROCESSOR}      PROJECT_PROCESSOR_UPPER)
-string (TOLOWER ${MACHINE}                PROJECT_MACHINE)
-string (TOUPPER ${MACHINE}                PROJECT_MACHINE_UPPER)
+
+if (DEFINED MACHINE)
+  # handle if '-' in machine name
+  string (REPLACE "-" "_" MACHINE ${MACHINE})
+  message ("-- Machine: ${MACHINE}")
+  string (TOLOWER ${MACHINE}                PROJECT_MACHINE)
+  string (TOUPPER ${MACHINE}                PROJECT_MACHINE_UPPER)
+endif (DEFINED MACHINE)
 
 option (WITH_STATIC_LIB "Build with a static library" ON)
 
diff --git a/lib/system/freertos/CMakeLists.txt b/lib/system/freertos/CMakeLists.txt
index 246bc4a..cf4d131 100644
--- a/lib/system/freertos/CMakeLists.txt
+++ b/lib/system/freertos/CMakeLists.txt
@@ -15,8 +15,8 @@ collect (PROJECT_LIB_SOURCES irq.c)
 collect (PROJECT_LIB_SOURCES shmem.c)
 collect (PROJECT_LIB_SOURCES time.c)
 
-if(EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/${PROJECT_VENDOR})
-    add_subdirectory(${PROJECT_VENDOR})
-elseif(EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/${PROJECT_MACHINE})
-  add_subdirectory(${PROJECT_MACHINE})
-endif(EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/${PROJECT_VENDOR})
+if (DEFINED PROJECT_MACHINE)
+  if (EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/${PROJECT_MACHINE})
+    add_subdirectory(${PROJECT_MACHINE})
+  endif (EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/${PROJECT_MACHINE})
+endif (DEFINED PROJECT_MACHINE)
diff --git a/lib/system/generic/CMakeLists.txt b/lib/system/generic/CMakeLists.txt
index 246bc4a..cf4d131 100644
--- a/lib/system/generic/CMakeLists.txt
+++ b/lib/system/generic/CMakeLists.txt
@@ -15,8 +15,8 @@ collect (PROJECT_LIB_SOURCES irq.c)
 collect (PROJECT_LIB_SOURCES shmem.c)
 collect (PROJECT_LIB_SOURCES time.c)
 
-if(EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/${PROJECT_VENDOR})
-    add_subdirectory(${PROJECT_VENDOR})
-elseif(EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/${PROJECT_MACHINE})
-  add_subdirectory(${PROJECT_MACHINE})
-endif(EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/${PROJECT_VENDOR})
+if (DEFINED PROJECT_MACHINE)
+  if (EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/${PROJECT_MACHINE})
+    add_subdirectory(${PROJECT_MACHINE})
+  endif (EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/${PROJECT_MACHINE})
+endif (DEFINED PROJECT_MACHINE)
diff --git a/test/system/freertos/CMakeLists.txt b/test/system/freertos/CMakeLists.txt
index 07717fa..05aef0e 100644
--- a/test/system/freertos/CMakeLists.txt
+++ b/test/system/freertos/CMakeLists.txt
@@ -8,7 +8,8 @@ collect (PROJECT_LIB_TESTS sleep.c)
 
 collect (PROJECT_LIB_API_TEST threads.c)
 
-if (EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/${PROJECT_MACHINE})
-  add_subdirectory(${PROJECT_MACHINE})
-endif (EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/${PROJECT_MACHINE})
-
+if (DEFINED PROJECT_MACHINE)
+  if (EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/${PROJECT_MACHINE})
+    add_subdirectory(${PROJECT_MACHINE})
+  endif (EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/${PROJECT_MACHINE})
+endif (DEFINED PROJECT_MACHINE)
diff --git a/test/system/generic/CMakeLists.txt b/test/system/generic/CMakeLists.txt
index a3ce25d..e899718 100644
--- a/test/system/generic/CMakeLists.txt
+++ b/test/system/generic/CMakeLists.txt
@@ -7,7 +7,9 @@ collect (PROJECT_LIB_TESTS threads.c)
 
 collect (PROJECT_LIB_TEST_ALL threads.c)
 
-if (EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/${PROJECT_MACHINE})
-  add_subdirectory(${PROJECT_MACHINE})
-endif (EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/${PROJECT_MACHINE})
+if (DEFINED PROJECT_MACHINE)
+  if (EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/${PROJECT_MACHINE})
+    add_subdirectory(${PROJECT_MACHINE})
+  endif (EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/${PROJECT_MACHINE})
+endif (DEFINED PROJECT_MACHINE)
 
diff --git a/test/system/linux/CMakeLists.txt b/test/system/linux/CMakeLists.txt
index e8d03c7..a39048b 100644
--- a/test/system/linux/CMakeLists.txt
+++ b/test/system/linux/CMakeLists.txt
@@ -10,7 +10,8 @@ collect (PROJECT_LIB_TESTS irq.c)
 
 collect (PROJECT_LIB_API_TEST threads.c)
 
-if (EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/${PROJECT_MACHINE})
-  add_subdirectory(${PROJECT_MACHINE})
-endif (EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/${PROJECT_MACHINE})
-
+if (DEFINED PROJECT_MACHINE)
+  if (EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/${PROJECT_MACHINE})
+    add_subdirectory(${PROJECT_MACHINE})
+  endif (EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/${PROJECT_MACHINE})
+endif (DEFINED PROJECT_MACHINE)
diff --git a/test/system/zephyr/CMakeLists.txt b/test/system/zephyr/CMakeLists.txt
index dac400c..fe5f8ef 100644
--- a/test/system/zephyr/CMakeLists.txt
+++ b/test/system/zephyr/CMakeLists.txt
@@ -6,7 +6,9 @@ collect (PROJECT_LIB_TESTS threads.c)
 
 collect (PROJECT_LIB_API_TEST threads.c)
 
-if (EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/${PROJECT_MACHINE})
-  add_subdirectory(${PROJECT_MACHINE})
-endif (EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/${PROJECT_MACHINE})
+if (DEFINED PROJECT_MACHINE)
+  if (EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/${PROJECT_MACHINE})
+    add_subdirectory(${PROJECT_MACHINE})
+  endif (EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/${PROJECT_MACHINE})
+endif (DEFINED PROJECT_MACHINE)