diff --git a/repos/base-hw/src/lib/base/thread_bootstrap.cc b/repos/base-hw/src/lib/base/thread_bootstrap.cc
index 48e0754f4a..df7e82e0e1 100644
--- a/repos/base-hw/src/lib/base/thread_bootstrap.cc
+++ b/repos/base-hw/src/lib/base/thread_bootstrap.cc
@@ -46,12 +46,15 @@ void prepare_init_main_thread()
 	 */
 	Native_utcb * utcb = Thread::myself()->utcb();
 	_parent_cap = Capability_space::import(utcb->cap_get(Native_utcb::PARENT));
+	Kernel::ack_cap(Capability_space::capid(_parent_cap));
 
 	Untyped_capability ds_cap =
 		Capability_space::import(utcb->cap_get(Native_utcb::UTCB_DATASPACE));
 	_main_thread_utcb_ds = reinterpret_cap_cast<Ram_dataspace>(ds_cap);
+	Kernel::ack_cap(Capability_space::capid(_main_thread_utcb_ds));
 
 	_main_thread_cap = Capability_space::import(utcb->cap_get(Native_utcb::THREAD_MYSELF));
+	Kernel::ack_cap(Capability_space::capid(_main_thread_cap));
 }
 
 
@@ -83,4 +86,6 @@ void Thread::_thread_bootstrap()
 {
 	Kernel::capid_t capid = myself()->utcb()->cap_get(Native_utcb::THREAD_MYSELF);
 	native_thread().cap = Capability_space::import(capid);
+	if (native_thread().cap.valid())
+		Kernel::ack_cap(Capability_space::capid(native_thread().cap));
 }