diff --git a/src/Makefile.in b/src/Makefile.in
index fbaa7356f43..6e27031c407 100644
--- a/src/Makefile.in
+++ b/src/Makefile.in
@@ -47,4 +47,5 @@ xmakefile: ymakefile config.h
 	rm -f junk.c
 
 tags TAGS:
-	etags [a-z]*.h [a-z]*.c ../lisp/[a-z]*.el ../lisp/term/[a-z]*.el
+	etags [a-z]*.h [a-z]*.c ../lisp/[a-z]*.el ../lisp/term/[a-z]*.el \
+	      ../external-lisp/*.el