--- php-5.6.40/acinclude.m4	2021-01-30 21:37:56.612413293 +0100
+++ php-5.6.40/acinclude.m4	2021-01-30 23:47:05.071091270 +0100
@@ -2212,6 +2212,8 @@
   if test "$PKG_CONFIG icu-io --atleast-version=60"; then
     ICU_CFLAGS="$ICU_CFLAGS -DU_HIDE_OBSOLETE_UTF_OLD_H=1"
   fi
+
+  ICU_CFLAGS="$ICU_CFLAGS -DU_DEFINE_FALSE_AND_TRUE=1"
 ])
 
 dnl