diff --git a/doc/Makefile.am b/doc/Makefile.am
index 6042b2994f..8c1e3fb85b 100644
--- a/doc/Makefile.am
+++ b/doc/Makefile.am
@@ -55,7 +55,7 @@ include images.mk
 all-local:
 	@rm -f images.tmp; \
 	echo $(ECHO_N) 'EXTRA_DIST += ' > images.tmp; \
-	(cd $(srcdir) && find ./img -type f -print | cut -d/ -f2- | grep -v '~' sort | tr '\n' ' ') >> images.tmp && \
+	(cd $(srcdir) && find ./img -type f -print | cut -d/ -f2- | grep -v '~' | sort | tr '\n' ' ') >> images.tmp && \
 	echo >> images.tmp && \
 	if ! cmp "$(srcdir)/images.mk" images.tmp >/dev/null; then \
 	   echo "warning: new images added to '$(srcdir)/images.mk'"; \