diff --git a/configure.ac b/configure.ac
index 0e0fe45..587283c 100644
--- a/configure.ac
+++ b/configure.ac
@@ -7,6 +7,7 @@ AC_CANONICAL_HOST
 AM_INIT_AUTOMAKE(1.6 dist-xz -Wno-portability)
 m4_ifdef([AM_SILENT_RULES], [AM_SILENT_RULES([yes])])
 
+AC_USE_SYSTEM_EXTENSIONS
 AC_C_BIGENDIAN
 AC_PROG_CC
 AM_PROG_AS
diff --git a/src/modules/loaders/loader_svg.c b/src/modules/loaders/loader_svg.c
index 7fe9780..31246ce 100644
--- a/src/modules/loaders/loader_svg.c
+++ b/src/modules/loaders/loader_svg.c
@@ -1,4 +1,3 @@
-#define _GNU_SOURCE             /* memmem() */
 #include "config.h"
 #include "Imlib2_Loader.h"
 
diff --git a/src/modules/loaders/loader_xbm.c b/src/modules/loaders/loader_xbm.c
index 77f8fe3..a43e7b9 100644
--- a/src/modules/loaders/loader_xbm.c
+++ b/src/modules/loaders/loader_xbm.c
@@ -1,7 +1,6 @@
 /*
  * XBM loader
  */
-#define _GNU_SOURCE             /* memmem() */
 #include "config.h"
 #include "Imlib2_Loader.h"
 
diff --git a/src/modules/loaders/loader_xpm.c b/src/modules/loaders/loader_xpm.c
index 7a96c86..247f67b 100644
--- a/src/modules/loaders/loader_xpm.c
+++ b/src/modules/loaders/loader_xpm.c
@@ -1,4 +1,3 @@
-#define _GNU_SOURCE             /* memmem() */
 #include "config.h"
 #include "Imlib2_Loader.h"