diff --git a/src/stdio/getw.c b/src/stdio/getw.c
index de9e985a..73d2c0d5 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 137832ee..a6d24292 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)