diff --git a/configure.ac b/configure.ac
index 25a83628..4e29f69b 100644
--- a/configure.ac
+++ b/configure.ac
@@ -270,8 +270,8 @@ supported_gfx=""
 dnl Platform-specific Makefile setup
 dnl ================================
 AS_CASE(["$host"],
-    [*-*-linux*|*-*-cygwin*|*-gnu*], [WM_OSDEP="linux" ; CPPFLAGS="$CPPFLAGS -D_XOPEN_SOURCE=600"],
-    [*-*-freebsd*|*-k*bsd-gnu*],     [WM_OSDEP="bsd"   ; CPPFLAGS="$CPPFLAGS -D_XOPEN_SOURCE=600 -DFREEBSD"],
+    [*-*-linux*|*-*-cygwin*|*-gnu*], [WM_OSDEP="linux" ; CPPFLAGS="$CPPFLAGS -D_XOPEN_SOURCE=700"],
+    [*-*-freebsd*|*-k*bsd-gnu*],     [WM_OSDEP="bsd"   ; CPPFLAGS="$CPPFLAGS -D_XOPEN_SOURCE=700 -DFREEBSD"],
     [*-*-netbsd*],                   [WM_OSDEP="bsd"   ; CPPFLAGS="$CPPFLAGS -DNETBSD"],
     [*-*-openbsd*],                  [WM_OSDEP="bsd"   ; CPPFLAGS="$CPPFLAGS -DOPENBSD"],
     [*-*-dragonfly*],                [WM_OSDEP="bsd"   ; CPPFLAGS="$CPPFLAGS -DDRAGONFLYBSD"],