1 files changed, 1 insertions, 0 deletions
diff --git a/configure b/configure
index b56575d7b7..78347b1dad 100755
--- a/configure
+++ b/configure
@@ -3564,6 +3564,7 @@ echores "$_vsscanf"
 
 echocheck "swab()"
 cat > $TMPC << EOF
+#define _XOPEN_SOURCE
 #include <unistd.h>
 int main(void) { swab(0, 0, 0); return 0; }
 EOF