diff --git a/configure.ac b/configure.ac
index 8e143f23..b9a15da0 100644
--- a/configure.ac
+++ b/configure.ac
@@ -26,6 +26,9 @@ if test "$clock" = "yes"; then
 	AC_DEFINE([ENABLE_CLOCK], [1], [enables clock screen])
 fi
 
+# OSX needs at least 500 for ncursesw specific functions
+CPPFLAGS="$CPPFLAGS -D_XOPEN_SOURCE=700"
+
 dnl ================================
 dnl = checking for -std=c++14 flag =
 dnl ================================