diff --git a/src/dwarfs/worker_group.cpp b/src/dwarfs/worker_group.cpp
index d3f3f678..117411a2 100644
--- a/src/dwarfs/worker_group.cpp
+++ b/src/dwarfs/worker_group.cpp
@@ -112,7 +112,7 @@ class basic_worker_group : public worker_group::impl, private Policy {
   /**
    * Check whether the worker group is still running
    */
-  bool running() const { return running_; }
+  bool running() const override { return running_; }
 
   /**
    * Add a new job to the worker group