--- a/doc/src/sgml/Makefile
+++ b/doc/src/sgml/Makefile
@@ -76,6 +76,7 @@ override SPFLAGS += -wall -wno-unused-param -wno-empty -wfully-tagged
 man distprep-man: man-stamp
 
 man-stamp: stylesheet-man.xsl postgres.xml
+	$(XMLLINT) --noout --valid postgres.xml
 	$(XSLTPROC) $(XSLTPROCFLAGS) $(XSLTPROC_MAN_FLAGS) $^
 	touch $@
 
@@ -252,11 +253,13 @@ endif
 xslthtml: xslthtml-stamp
 
 xslthtml-stamp: stylesheet.xsl postgres.xml
+	$(XMLLINT) --noout --valid postgres.xml
 	$(XSLTPROC) $(XSLTPROCFLAGS) $(XSLTPROC_HTML_FLAGS) $^
 	cp $(srcdir)/stylesheet.css html/
 	touch $@
 
 htmlhelp: stylesheet-hh.xsl postgres.xml
+	$(XMLLINT) --noout --valid postgres.xml
 	$(XSLTPROC) $(XSLTPROCFLAGS) $^
 
 %-A4.fo.tmp: stylesheet-fo.xsl %.xml
@@ -279,6 +282,7 @@ XMLLINT = xmllint
 
 epub: postgres.epub
 postgres.epub: postgres.xml
+	$(XMLLINT) --noout --valid $<
 	$(DBTOEPUB) $<