diff --git a/configure.ac b/configure.ac
index 19396204..7ea60298 100644
--- a/configure.ac
+++ b/configure.ac
@@ -42,6 +42,7 @@ AC_CHECK_HEADERS([fcntl.h stdlib.h string.h sys/socket.h time.h sys/time.h syslo
 
 # Source characteristics
 AC_DEFINE([_XOPEN_SOURCE], [700], [Uses X/Open and POSIX APIs])
+AC_DEFINE([__BSD_VISIBLE], [1], [Uses BSD-specific APIs (if available)])
 
 # Check for whether math library is required
 AC_CHECK_LIB([m], [cos],