diff --git a/src/Makefile.am b/src/Makefile.am
index dd13940..4e1fdb1 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -2,4 +2,5 @@ bin_PROGRAMS = sermon
 BUILT_SOURCES = sermon_lexer.c sermon_parser.c sermon_parser.h
 AM_YFLAGS = -d --location
 sermon_SOURCES = sermon_lexer.l sermon_parser.y sermon_util.c
+CLEANFILES = sermon_lexer.c sermon_parser.c sermon_parser.h
 LIBS = $(LEXLIB)