diff --git a/scripts/phpize.m4 b/scripts/phpize.m4
index 384d44cd9bb..30a9661c69c 100644
--- a/scripts/phpize.m4
+++ b/scripts/phpize.m4
@@ -81,6 +81,7 @@ install_targets="install-modules install-headers"
 phplibdir="`pwd`/modules"
 CPPFLAGS="$CPPFLAGS -DHAVE_CONFIG_H"
 CFLAGS_CLEAN='$(CFLAGS)'
+CXXFLAGS_CLEAN='$(CXXFLAGS)'
 
 test "$prefix" = "NONE" && prefix="/usr/local"
 test "$exec_prefix" = "NONE" && exec_prefix='$(prefix)'
@@ -103,6 +104,7 @@ PHP_SUBST(CPP)
 PHP_SUBST(CPPFLAGS)
 PHP_SUBST(CXX)
 PHP_SUBST(CXXFLAGS)
+PHP_SUBST(CXXFLAGS_CLEAN)
 PHP_SUBST(EXTENSION_DIR)
 PHP_SUBST(PHP_EXECUTABLE)
 PHP_SUBST(EXTRA_LDFLAGS)