diff --git a/pisi-spec.rng b/pisi-spec.rng
index 9c602a0c..7e6acd70 100644
--- a/pisi-spec.rng
+++ b/pisi-spec.rng
@@ -32,9 +32,9 @@
             <optional>
                 <ref name="Icon"/>
             </optional>
-            <oneOrMore>
+            <zeroOrMore>
                 <ref name="IsA"/>
-            </oneOrMore>
+            </zeroOrMore>
             <optional>
                 <ref name="PartOf"/>
             </optional>