diff --git a/REB/REB.csl b/REB/REB.csl
index fe7061e..bf2a262 100644
--- a/REB/REB.csl
+++ b/REB/REB.csl
@@ -459,7 +459,7 @@
   <macro name="publicationCollection">
     <group prefix="(" suffix=")" delimiter=" ">
       <text variable="collection-title" form="short"/>
-      <text variable="collection-number"/>
+      <number variable="collection-number"/>
     </group>
   </macro>