diff --git a/CMakeLists.txt b/CMakeLists.txt
index cce24fe..fb4945d 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -24,8 +24,8 @@ include_directories(${PROJECT_BINARY_DIR} ${PROJECT_SOURCE_DIR}	${LIBMPDCLIENT_I
 
 include(CheckCSourceCompiles)
 
-set(CMAKE_C_FLAGS "-std=gnu99 -Wall")
-set(CMAKE_C_FLAGS_DEBUG "-ggdb -pedantic")
+set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -std=gnu99 -Wall")
+set(CMAKE_C_FLAGS_DEBUG "${CMAKE_C_FLAGS_DEBUG} -ggdb -pedantic")
 if(WITH_IPV6)
     set_property(DIRECTORY APPEND PROPERTY COMPILE_DEFINITIONS NS_ENABLE_IPV6)
 endif()