diff --git a/CMakeLists.txt b/CMakeLists.txt
index 4882db54..5ff66a6d 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -39,7 +39,7 @@ elseif(${CMAKE_CXX_STANDARD} LESS 11)
 endif()
 
 # Backwards comptability
-if(OS_FSFW)
+if(OS_FSFW AND NOT FSFW_OSAL)
     message(WARNING "Please pass the FSFW OSAL as FSFW_OSAL instead of OS_FSFW")
     set(FSFW_OSAL OS_FSFW)
 endif()
@@ -63,35 +63,28 @@ endif()
 set(FSFW_OSAL_DEFINITION FSFW_OSAL_HOST)
 
 if(FSFW_OSAL MATCHES host)
-	set(OS_FSFW_NAME "Host")
+    set(OS_FSFW_NAME "Host")
+    set(FSFW_OSAL_HOST ON)
 elseif(FSFW_OSAL MATCHES linux)
-	set(OS_FSFW_NAME "Linux")
-	set(FSFW_OSAL_DEFINITION FSFW_OSAL_LINUX)
+    set(OS_FSFW_NAME "Linux")
+    set(FSFW_OSAL_LINUX ON)
 elseif(FSFW_OSAL MATCHES freertos)
-	set(OS_FSFW_NAME "FreeRTOS")
-	set(FSFW_OSAL_DEFINITION FSFW_OSAL_FREERTOS)
-	target_link_libraries(${LIB_FSFW_NAME} PRIVATE
+    set(OS_FSFW_NAME "FreeRTOS")
+    set(FSFW_OSAL_FREERTOS ON)
+    target_link_libraries(${LIB_FSFW_NAME} PRIVATE
         ${LIB_OS_NAME}
-	)
+    )
 elseif(FSFW_OSAL STREQUAL rtems)
-	set(OS_FSFW_NAME "RTEMS")
-    set(FSFW_OSAL_DEFINITION FSFW_OSAL_RTEMS)
+    set(OS_FSFW_NAME "RTEMS")
+    set(FSFW_OSAL_RTEMS ON)
 else()
-	message(WARNING 
-		"Invalid operating system for FSFW specified! Setting to host.."
-	)
-	set(OS_FSFW_NAME "Host")
-	set(OS_FSFW "host")
+    message(WARNING
+        "Invalid operating system for FSFW specified! Setting to host.."
+    )
+    set(OS_FSFW_NAME "Host")
+    set(OS_FSFW "host")
 endif()
 
-target_compile_definitions(${LIB_FSFW_NAME} PRIVATE
-    ${FSFW_OSAL_DEFINITION}
-)
-
-target_compile_definitions(${LIB_FSFW_NAME} INTERFACE
-    ${FSFW_OSAL_DEFINITION}
-)
-
 message(STATUS "Compiling FSFW for the ${OS_FSFW_NAME} operating system.")
 
 add_subdirectory(src)
diff --git a/src/fsfw/FSFW.h.in b/src/fsfw/FSFW.h.in
index 4d4b8aee..f0eb9365 100644
--- a/src/fsfw/FSFW.h.in
+++ b/src/fsfw/FSFW.h.in
@@ -3,6 +3,11 @@
 
 #include "FSFWConfig.h"
 
+#cmakedefine FSFW_OSAL_RTEMS
+#cmakedefine FSFW_OSAL_FREERTOS
+#cmakedefine FSFW_OSAL_LINUX
+#cmakedefine FSFW_OSAL_HOST
+
 #cmakedefine FSFW_ADD_RMAP
 #cmakedefine FSFW_ADD_DATALINKLAYER
 #cmakedefine FSFW_ADD_TMSTORAGE