diff --git a/CMakeLists.txt b/CMakeLists.txt
index 5bab518..1feb434 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -23,6 +23,7 @@ if (NOT CMAKE_BUILD_TYPE)
 	     FORCE)
 endif (NOT CMAKE_BUILD_TYPE)
 
+add_definitions(-D_GNU_SOURCE)
 find_package(DWARF REQUIRED)
 
 _set_fancy(LIB_INSTALL_DIR "${EXEC_INSTALL_PREFIX}${CMAKE_INSTALL_PREFIX}/${__LIB}" "libdir")
diff --git a/dwarves.c b/dwarves.c
index b82ad3a..2b5cf90 100644
--- a/dwarves.c
+++ b/dwarves.c
@@ -9,7 +9,6 @@
   published by the Free Software Foundation.
 */
 
-#define _GNU_SOURCE
 #include <assert.h>
 #include <dirent.h>
 #include <dwarf.h>
diff --git a/pglobal.c b/pglobal.c
index 824276d..6e3dd39 100644
--- a/pglobal.c
+++ b/pglobal.c
@@ -6,7 +6,6 @@
  * by the Free Software Foundation.
  */
 
-#define _GNU_SOURCE
 #include <argp.h>
 #include <malloc.h>
 #include <search.h>
diff --git a/syscse.c b/syscse.c
index 7b94f3e..c257306 100644
--- a/syscse.c
+++ b/syscse.c
@@ -8,7 +8,6 @@
   published by the Free Software Foundation.
 */
 
-#define _GNU_SOURCE
 #include <argp.h>
 #include <assert.h>
 #include <stdio.h>