diff --git a/Makefile.am b/Makefile.am
index 41589426..896b5056 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -11,7 +11,7 @@ EXTRA_DIST = oniguruma.pc.in HISTORY README_japanese README.md \
 	doc/API doc/API.ja doc/RE doc/RE.ja doc/FAQ doc/FAQ.ja \
 	doc/CALLOUTS.BUILTIN doc/CALLOUTS.BUILTIN.ja \
 	doc/CALLOUTS.API doc/CALLOUTS.API.ja \
-	doc/SYNTAX.md doc/UNICODE_PROPERTIES \
+	doc/SYNTAX.md doc/onig_syn_md.c doc/UNICODE_PROPERTIES \
 	src/Makefile.windows src/config.h.windows.in \
 	src/config.h.win32 src/config.h.win64 \
 	test/test.sh test/CMakeLists.txt \