diff --git a/src/util/cancellable.cpp b/src/util/cancellable.cpp
index f3294e5797..84ab3481e3 100644
--- a/src/util/cancellable.cpp
+++ b/src/util/cancellable.cpp
@@ -27,9 +27,13 @@ void cancellation_token_cell::cancel(std::shared_ptr<cancellable> const &) {
 
 void cancellation_token_cell::gc() {
     unique_lock<mutex> lock(m_mutex);
-    m_children.erase(std::remove_if(m_children.begin(), m_children.end(),
-                                    [] (std::weak_ptr<cancellable> const & c) { return c.expired(); }),
-                     m_children.end());
+    m_expired_children++;
+    if (m_expired_children > m_children.size()/2) {
+        m_children.erase(std::remove_if(m_children.begin(), m_children.end(),
+                                        [](std::weak_ptr<cancellable> const &c) { return c.expired(); }),
+                         m_children.end());
+        m_expired_children = 0;
+    }
 }
 
 void cancellation_token_cell::add_child(std::weak_ptr<cancellable> const & c) {
diff --git a/src/util/cancellable.h b/src/util/cancellable.h
index 2003640d78..d8ca6ab757 100644
--- a/src/util/cancellable.h
+++ b/src/util/cancellable.h
@@ -25,6 +25,7 @@ class cancellation_token_cell : public cancellable {
     mutex m_mutex;
     atomic_bool m_cancelled;
     std::vector<std::weak_ptr<cancellable>> m_children;
+    unsigned m_expired_children = 0;
     cancellation_token m_parent;
 
     friend cancellation_token mk_cancellation_token(cancellation_token const &);