diff --git a/doc/ref/Makefile.am b/doc/ref/Makefile.am
index d771c2881..2f218a565 100644
--- a/doc/ref/Makefile.am
+++ b/doc/ref/Makefile.am
@@ -85,7 +85,13 @@ guile_TEXINFOS = preface.texi			\
 
 ETAGS_ARGS = $(info_TEXINFOS) $(guile_TEXINFOS)
 
-EXTRA_DIST = ChangeLog-2008
+PICTURES = hierarchy.eps \
+	   hierarchy.pdf \
+	   hierarchy.png \
+	   hierarchy.txt \
+	   mop.text
+
+EXTRA_DIST = ChangeLog-2008 $(PICTURES)
 
 include $(top_srcdir)/am/pre-inst-guile