diff --git a/src/relaxng/settings.rnc b/src/relaxng/settings.rnc
index e23cbdd6cd..742e137738 100644
--- a/src/relaxng/settings.rnc
+++ b/src/relaxng/settings.rnc
@@ -153,7 +153,7 @@ element settings {
       attribute lower_left { list { xsd:double+ } }) &
     (element upper_right { list { xsd:double+ } } |
       attribute upper_right { list { xsd:double+ } })
-  }+ &
+  }* &
 
   element uniform_fs{
     (element dimension { list { xsd:positiveInteger+ } } |
diff --git a/src/relaxng/settings.rng b/src/relaxng/settings.rng
index 38acea5985..39bed4a62f 100644
--- a/src/relaxng/settings.rng
+++ b/src/relaxng/settings.rng
@@ -625,7 +625,7 @@
         <data type="positiveInteger"/>
       </element>
     </optional>
-    <oneOrMore>
+    <zeroOrMore>
       <element name="volume_calc">
         <interleave>
           <choice>
@@ -694,7 +694,7 @@
           </choice>
         </interleave>
       </element>
-    </oneOrMore>
+    </zeroOrMore>
     <optional>
       <element name="uniform_fs">
         <interleave>