--- php-5.6.40/acinclude.m4	2021-01-31 11:00:18.549678215 +0100
+++ php-5.6.40/acinclude.m4	2021-01-31 11:01:50.030900044 +0100
@@ -2212,6 +2212,9 @@
   if test "$PKG_CONFIG icu-io --atleast-version=60"; then
     ICU_CFLAGS="$ICU_CFLAGS -DU_HIDE_OBSOLETE_UTF_OLD_H=1"
   fi
+
+  ICU_CFLAGS="$ICU_CFLAGS -DU_DEFINE_FALSE_AND_TRUE=1"
+  ICU_CXXFLAGS="$ICU_CXXFLAGS -DU_DEFINE_FALSE_AND_TRUE=1"
 ])
 
 dnl