--- a/ext/intl/config.m4
+++ b/ext/intl/config.m4
@@ -9,7 +9,7 @@
   PHP_SETUP_ICU(INTL_SHARED_LIBADD)
   PHP_SUBST(INTL_SHARED_LIBADD)
   PHP_REQUIRE_CXX()
-  INTL_COMMON_FLAGS="$ICU_CFLAGS -Wno-write-strings -D__STDC_LIMIT_MACROS -DZEND_ENABLE_STATIC_TSRMLS_CACHE=1"
+  INTL_COMMON_FLAGS="$ICU_CFLAGS -Wno-write-strings -D__STDC_LIMIT_MACROS -DZEND_ENABLE_STATIC_TSRMLS_CACHE=1 -DU_DEFINE_FALSE_AND_TRUE=1"
   PHP_NEW_EXTENSION(intl, php_intl.c \
     intl_error.c \
     intl_convert.c \
@@ -84,7 +84,7 @@
     breakiterator/codepointiterator_internal.cpp \
     breakiterator/codepointiterator_methods.cpp"
 
-  PHP_INTL_CPP_FLAGS="$ICU_CXXFLAGS -Wno-write-strings -D__STDC_LIMIT_MACROS -DZEND_ENABLE_STATIC_TSRMLS_CACHE=1"
+  PHP_INTL_CPP_FLAGS="$ICU_CXXFLAGS -Wno-write-strings -D__STDC_LIMIT_MACROS -DZEND_ENABLE_STATIC_TSRMLS_CACHE=1 -DU_DEFINE_FALSE_AND_TRUE=1"
   if test "$ext_shared" = "no"; then
     PHP_ADD_SOURCES(PHP_EXT_DIR(intl), $PHP_INTL_CPP_SOURCES, $PHP_INTL_CPP_FLAGS)
   else