diff --git a/include/dwarfs/internal/worker_group.h b/include/dwarfs/internal/worker_group.h
index 48299e20..b540ddb5 100644
--- a/include/dwarfs/internal/worker_group.h
+++ b/include/dwarfs/internal/worker_group.h
@@ -28,9 +28,9 @@
 #include <future>
 #include <limits>
 #include <memory>
+#include <optional>
 #include <utility>
 
-#include <folly/Expected.h>
 #include <folly/Function.h>
 
 namespace dwarfs {
@@ -87,10 +87,15 @@ class worker_group {
 
   size_t size() const { return impl_->size(); }
   size_t queue_size() const { return impl_->queue_size(); }
-  folly::Expected<std::chrono::nanoseconds, std::error_code>
-  get_cpu_time() const {
-    return impl_->get_cpu_time();
+
+  std::chrono::nanoseconds get_cpu_time(std::error_code& ec) const {
+    return impl_->get_cpu_time(ec);
   }
+
+  std::optional<std::chrono::nanoseconds> try_get_cpu_time() const {
+    return impl_->try_get_cpu_time();
+  }
+
   bool set_affinity(std::vector<int> const& cpus) {
     return impl_->set_affinity(cpus);
   }
@@ -111,8 +116,10 @@ class worker_group {
     virtual bool add_moveonly_job(moveonly_job_t&& job) = 0;
     virtual size_t size() const = 0;
     virtual size_t queue_size() const = 0;
-    virtual folly::Expected<std::chrono::nanoseconds, std::error_code>
-    get_cpu_time() const = 0;
+    virtual std::chrono::nanoseconds
+    get_cpu_time(std::error_code& ec) const = 0;
+    virtual std::optional<std::chrono::nanoseconds>
+    try_get_cpu_time() const = 0;
     virtual bool set_affinity(std::vector<int> const& cpus) = 0;
   };
 
diff --git a/include/dwarfs/thread_pool.h b/include/dwarfs/thread_pool.h
index dacd7b95..baccd423 100644
--- a/include/dwarfs/thread_pool.h
+++ b/include/dwarfs/thread_pool.h
@@ -25,6 +25,7 @@
 #include <functional>
 #include <limits>
 #include <memory>
+#include <optional>
 #include <system_error>
 
 namespace dwarfs {
@@ -66,6 +67,7 @@ class thread_pool {
   void stop();
   void wait();
   bool running() const;
+  std::optional<std::chrono::nanoseconds> try_get_cpu_time() const;
   std::chrono::nanoseconds get_cpu_time() const;
   std::chrono::nanoseconds get_cpu_time(std::error_code& ec) const;
 
diff --git a/src/dwarfs/internal/worker_group.cpp b/src/dwarfs/internal/worker_group.cpp
index 669ef154..2cc7f83b 100644
--- a/src/dwarfs/internal/worker_group.cpp
+++ b/src/dwarfs/internal/worker_group.cpp
@@ -168,22 +168,28 @@ class basic_worker_group final : public worker_group::impl, private Policy {
     return jobs_.size();
   }
 
-  folly::Expected<std::chrono::nanoseconds, std::error_code>
-  get_cpu_time() const override {
+  std::chrono::nanoseconds get_cpu_time(std::error_code& ec) const override {
+    ec.clear();
+
     std::lock_guard lock(mx_);
     std::chrono::nanoseconds t{};
 
     for (auto const& w : workers_) {
-      std::error_code ec;
       t += os_.thread_get_cpu_time(w.get_id(), ec);
       if (ec) {
-        return folly::makeUnexpected(ec);
+        return {};
       }
     }
 
     return t;
   }
 
+  std::optional<std::chrono::nanoseconds> try_get_cpu_time() const override {
+    std::error_code ec;
+    auto t = get_cpu_time(ec);
+    return ec ? std::nullopt : std::make_optional(t);
+  }
+
   bool set_affinity(std::vector<int> const& cpus) override {
     if (cpus.empty()) {
       return false;
diff --git a/src/dwarfs/scanner.cpp b/src/dwarfs/scanner.cpp
index cd6167ae..3639efcf 100644
--- a/src/dwarfs/scanner.cpp
+++ b/src/dwarfs/scanner.cpp
@@ -647,7 +647,7 @@ void scanner_<LoggerPolicy>::scan(
   wg_.wait();
 
   LOG_INFO << "scanning CPU time: "
-           << time_with_unit(wg_.get_cpu_time().value_or(0ns));
+           << time_with_unit(wg_.try_get_cpu_time().value_or(0ns));
 
   dump_state(kEnvVarDumpFilesRaw, "raw files", fa,
              [&fs](auto& os) { fs.dump(os); });
@@ -827,10 +827,10 @@ void scanner_<LoggerPolicy>::scan(
     wg_ordering.wait();
 
     LOG_INFO << "total ordering CPU time: "
-             << time_with_unit(wg_ordering.get_cpu_time().value_or(0ns));
+             << time_with_unit(wg_ordering.try_get_cpu_time().value_or(0ns));
 
     LOG_INFO << "total segmenting CPU time: "
-             << time_with_unit(wg_blockify.get_cpu_time().value_or(0ns));
+             << time_with_unit(wg_blockify.try_get_cpu_time().value_or(0ns));
   }
 
   // seg.finish();
diff --git a/src/dwarfs/thread_pool.cpp b/src/dwarfs/thread_pool.cpp
index 55aa81b7..a80694ab 100644
--- a/src/dwarfs/thread_pool.cpp
+++ b/src/dwarfs/thread_pool.cpp
@@ -43,13 +43,7 @@ void thread_pool::wait() { wg_->wait(); }
 bool thread_pool::running() const { return wg_->running(); }
 
 std::chrono::nanoseconds thread_pool::get_cpu_time(std::error_code& ec) const {
-  auto rv = wg_->get_cpu_time();
-  if (rv) {
-    ec.clear();
-    return rv.value();
-  }
-  ec = rv.error();
-  return {};
+  return wg_->get_cpu_time(ec);
 }
 
 std::chrono::nanoseconds thread_pool::get_cpu_time() const {
@@ -61,4 +55,8 @@ std::chrono::nanoseconds thread_pool::get_cpu_time() const {
   return rv;
 }
 
+std::optional<std::chrono::nanoseconds> thread_pool::try_get_cpu_time() const {
+  return wg_->try_get_cpu_time();
+}
+
 } // namespace dwarfs