diff --git a/sample/Makefile b/sample/Makefile
index a10144f..7e8ab7b 100644
--- a/sample/Makefile
+++ b/sample/Makefile
@@ -1,7 +1,9 @@
 XBYAK_INC=../xbyak/xbyak.h
 CXX?=g++
 
-BOOST_EXIST=$(shell echo "#include <boost/spirit/core.hpp>" | $CXX -x c++ -c - 2>/dev/null && echo 1)
+#BOOST_EXIST=$(shell echo "#include <boost/spirit/core.hpp>" | $CXX -x c++ -c - 2>/dev/null && echo 1)
+# I don't know why the above code causes an error on GitHub action.
+BOOST_EXIST?=0
 UNAME_M=$(shell uname -m)
 
 ONLY_64BIT=0