diff --git a/osal/FreeRTOS/CountingSemaphore.cpp b/osal/FreeRTOS/CountingSemaphore.cpp
index adf3f23c..2b81848a 100644
--- a/osal/FreeRTOS/CountingSemaphore.cpp
+++ b/osal/FreeRTOS/CountingSemaphore.cpp
@@ -1,6 +1,8 @@
 #include <framework/osal/FreeRTOS/CountingSemaphore.h>
 #include <framework/serviceinterface/ServiceInterfaceStream.h>
 
+// Make sure #define configUSE_COUNTING_SEMAPHORES 1 is set in
+// free FreeRTOSConfig.h file.
 CountingSemaphore::CountingSemaphore(uint8_t count, uint8_t initCount):
 		count(count), initCount(initCount) {
 	handle = xSemaphoreCreateCounting(count, initCount);