diff --git a/src/stdio/getw.c b/src/stdio/getw.c
index de9e985ae53a5c9a2d60497d03c64d1a574a5f87..73d2c0d5c6c0914322903e0c30e3f93c0f9336cc 100644
--- a/src/stdio/getw.c
+++ b/src/stdio/getw.c
@@ -1,3 +1,4 @@
+#define _GNU_SOURCE
 #include <stdio.h>
 
 int getw(FILE *f)
diff --git a/src/stdio/putw.c b/src/stdio/putw.c
index 137832ee1b66f1fca9725bfe7d9e64026d73f02a..a6d2429278a67f3df5061c041fc113b1fd2d350e 100644
--- a/src/stdio/putw.c
+++ b/src/stdio/putw.c
@@ -1,3 +1,4 @@
+#define _GNU_SOURCE
 #include <stdio.h>
 
 int putw(int x, FILE *f)