diff --git a/lib/Makefile.am b/lib/Makefile.am
index a4d5138..4f30055 100644
--- a/lib/Makefile.am
+++ b/lib/Makefile.am
@@ -1,7 +1,7 @@
 
 lib_LTLIBRARIES = libcomedi.la
 
-noinst_HEADERS = calib_yacc.h comedi_errno.h libinternal.h
+noinst_HEADERS = calib_lex.h calib_yacc.h comedi_errno.h libinternal.h
 
 CLEANFILES = grammar.output