diff --git a/CMakeLists.txt b/CMakeLists.txt
index 848613fd7..9f4e8c0f9 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -176,7 +176,7 @@ if (NOT CMAKE_BUILD_TYPE)
 endif()
 
 # add_definitions() doesn't seem to let you say wich build type to apply it to
-set(CMAKE_C_FLAGS_DEBUG "${CMAKE_C_FLAGS_DEBUG} -DTORRENT_DEBUG")
+set(CMAKE_CXX_FLAGS_DEBUG "${CMAKE_CXX_FLAGS_DEBUG} -DTORRENT_DEBUG")
 if(UNIX)
 	set(CMAKE_C_FLAGS_RELWITHDEBINFO "-Os -g")
 	set(CMAKE_CXX_FLAGS_RELWITHDEBINFO "${CMAKE_C_FLAGS_RELWITHDEBINFO}")