diff --git a/Makefile b/Makefile
index b5c7dd9..f1d1b93 100644
--- a/Makefile
+++ b/Makefile
@@ -27,7 +27,7 @@
 test: linkcheck lint
 
 linkcheck: build
-	linkchecker --check-extern -a _book/
+	linkchecker -a _book/
 
 lint:
 	@echo "markdownlint(mdl) version: `mdl --version`"