diff --git a/packages/processor/index.ts b/packages/processor/index.ts
index d804c86..bddda08 100644
--- a/packages/processor/index.ts
+++ b/packages/processor/index.ts
@@ -415,7 +415,7 @@ export default abstract class ProcessorImpl<F extends DataFactory = DataFactory>
       .exhaustive()
   }
 
-  processFunctionCall(functionCall: sparqljs.FunctionCallExpression): sparqljs.FunctionCallExpression {
+  processFunctionCall(functionCall: sparqljs.FunctionCallExpression): sparqljs.Expression {
     return {
       ...functionCall,
       function: match(functionCall.function)