diff --git a/contrib/libtests/pngvalid.c b/contrib/libtests/pngvalid.c
index e66f2fa61..53170f85b 100644
--- a/contrib/libtests/pngvalid.c
+++ b/contrib/libtests/pngvalid.c
@@ -21,6 +21,7 @@
 #define _POSIX_SOURCE 1
 #define _ISOC99_SOURCE 1 /* For floating point */
 #define _GNU_SOURCE 1 /* For the floating point exception extension */
+#define _BSD_SOURCE 1 /* For the floating point exception extension */
 
 #include <signal.h>
 #include <stdio.h>