diff --git a/make-includes/build_lecture_rules.make b/make-includes/build_lecture_rules.make
index 01c8a53..9f30439 100755
--- a/make-includes/build_lecture_rules.make
+++ b/make-includes/build_lecture_rules.make
@@ -67,6 +67,7 @@
 ifneq ($(strip $(COMBINED)),)
 INSTALL_FILES+=$(COMBINED).pdf
 endif
+INSTALL_FILES+=$(wildcard *.mp3)
 #
 # List of standard "phony" build targets.
 #