diff --git a/doc/docutils/Makefile.am b/doc/docutils/Makefile.am
index 631ab7c06..eeec2fbf9 100644
--- a/doc/docutils/Makefile.am
+++ b/doc/docutils/Makefile.am
@@ -30,7 +30,7 @@ RSTFILES = \
 	overview.rst \
 	docapi.rst
 
-EXTRA_DIST = $(RSTFILES)
+EXTRA_DIST += $(RSTFILES)
 
 SPHINXOPTS      =
 SOURCEDIR       = $(srcdir)