diff --git a/src/protocol/mod.rs b/src/protocol/mod.rs
index 80cf2c2384e5bf2f619e58947a66d22db4d73ef3..518b5f07d699dd1f3800407424add0738a7c0751 100644
--- a/src/protocol/mod.rs
+++ b/src/protocol/mod.rs
@@ -128,7 +128,7 @@ impl ProtocolDescription {
 
         // By now we're sure that all of the arguments are correct. So create
         // the connector.
-        return Ok(Prompt::new(&self.types, &self.heap, definition_id, 0, arguments));
+        return Ok(Prompt::new(&self.types, &self.heap, definition_id, mono_index, arguments));
     }
 
     fn lookup_module_root(&self, module_name: &[u8]) -> Option<RootId> {