diff --git a/src/main/wacc/frontend/renamer.scala b/src/main/wacc/frontend/renamer.scala
index bbce1bb..4893d42 100644
--- a/src/main/wacc/frontend/renamer.scala
+++ b/src/main/wacc/frontend/renamer.scala
@@ -267,18 +267,24 @@ object renamer {
     * @return
     *   (flattenedProg, errors)
     */
+  private def renameFunction(funcScopePair: (FuncDecl, Scope)): IO[Chain[Error]] = {
+    val (FuncDecl(_, _, params, body), subscope) = funcScopePair
+    val paramErrors = params.foldMap(param => subscope.add(param.name))
+    IO(subscope.withSubscope { s => body.foldMap(rename(s)) })
+      .map(bodyErrors => paramErrors ++ bodyErrors)
+  }
+
   def rename(partialProg: PartialProgram): IO[(Program, Chain[Error])] = {
     given scope: Scope = Scope(mutable.Map.empty, Map.empty)
+
     for {
-      (main, chunks, errors) <- prepareGlobalScope(partialProg)
+      (main, chunks, globalErrors) <- prepareGlobalScope(partialProg)
       toRename = (main +: chunks).toList
-      res = (toRename zip scope.subscopes(toRename.size)).foldMap {
-        case (func @ FuncDecl(retType, name, params, body), subscope) =>
-          val paramErrors = params.foldMap { param => subscope.add(param.name) }
-          val bodyErrors = subscope.withSubscope { s => body.foldMap(rename(s)) }
-          paramErrors ++ bodyErrors
-      }
-    } yield (Program(chunks.toList, main.body)(main.pos), errors ++ res)
+      allErrors <- toRename
+        .zip(scope.subscopes(toRename.size))
+        .parFoldMapA(renameFunction)
+      // .map(x => x.combineAll)
+    } yield (Program(chunks.toList, main.body)(main.pos), globalErrors ++ allErrors)
   }
 
   /** Check scoping of all identifies in a given AST node.