diff --git a/CMakeLists.txt b/CMakeLists.txt
index d8e793c3a..14f235775 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -171,7 +171,7 @@ elseif(UNIX)
 	add_definitions(-DUSE_PTHREADS)
 
 	if(CMAKE_SYSTEM_NAME STREQUAL "Linux")
-		add_definitions(-D_BSD_SOURCE -D_POSIX_SOURCE -D_POSIX_C_SOURCE=200809L)
+		add_definitions(-D_GNU_SOURCE)
 	endif()
 	if(NOT APPLE AND NOT HAIKU)
 		set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -pthread")