diff --git a/configure.ac b/configure.ac
index 4b0ed882..dcae8b46 100644
--- a/configure.ac
+++ b/configure.ac
@@ -98,7 +98,7 @@ AX_CHECK_COMPILE_FLAG([-xc99],[CFLAGS="$CFLAGS -xc99"],[],[])
 AX_CHECK_COMPILE_FLAG([-Wall],[CFLAGS="$CFLAGS -Wall"],[],[])
 
 case "$host_os" in
-  linux* ) CFLAGS="$CFLAGS -D_BSD_SOURCE"
+  linux* ) CFLAGS="$CFLAGS -D_BSD_SOURCE -D_DEFAULT_SOURCE"
   ;;
   solaris* ) CFLAGS="$CFLAGS -D__EXTENSIONS__"  # for strdup() from <string.h>
   ;;