diff --git a/expat/doc/Makefile.am b/expat/doc/Makefile.am
index 3538d0dd..9d12923d 100644
--- a/expat/doc/Makefile.am
+++ b/expat/doc/Makefile.am
@@ -37,7 +37,7 @@ dist_man_MANS = xmlwf.1
 
 xmlwf.1: xmlwf.xml
 	-rm -f $@
-	test x$(DOCBOOK_TO_MAN) != x && $(DOCBOOK_TO_MAN) $<
+	test "x$(DOCBOOK_TO_MAN)" != x && $(DOCBOOK_TO_MAN) $<
 	test -f $@ || mv XMLWF.1 $@
 endif