diff --git a/configure.ac b/configure.ac
index a6cee7077f3bd05ae081109dc827f0b28d3e4f26..f1cd4ca50446447507e1603dfcdee9cbc9d867ca 100644
--- a/configure.ac
+++ b/configure.ac
@@ -921,7 +921,7 @@ else
 fi
 AC_SUBST(HavePapi)
 
-if test "$HAVE_DOCBOOK_XSL" = "" ||
+if test "$HAVE_DOCBOOK_XSL" = "NO" ||
    test "$XsltprocCmd" = ""
 then
     BUILD_DOCBOOK_HTML=NO