diff --git a/base-nova/src/base/thread/thread_nova.cc b/base-nova/src/base/thread/thread_nova.cc
index f62b609ab..26c754bb3 100644
--- a/base-nova/src/base/thread/thread_nova.cc
+++ b/base-nova/src/base/thread/thread_nova.cc
@@ -151,6 +151,11 @@ void Thread_base::start()
 		request_event_portal(_pager_cap, _tid.exc_pt_sel, PT_SEL_RECALL);
 	}
 
+	/* default: we don't accept any mappings or translations */
+	Utcb * utcb_obj = reinterpret_cast<Utcb *>(utcb());
+	utcb_obj->crd_rcv = Obj_crd();
+	utcb_obj->crd_xlt = Obj_crd();
+
 	/* request creation of SC to let thread run*/
 	env()->cpu_session()->resume(_thread_cap);
 }
diff --git a/base-nova/src/core/irq_session_component.cc b/base-nova/src/core/irq_session_component.cc
index 55c5bd5df..53d96e741 100644
--- a/base-nova/src/core/irq_session_component.cc
+++ b/base-nova/src/core/irq_session_component.cc
@@ -91,6 +91,11 @@ class Irq_thread : public Thread_base
 				throw Cpu_session::Thread_creation_failed();
 			}
 
+			/* default: we don't accept any mappings or translations */
+			Utcb * utcb_obj = reinterpret_cast<Utcb *>(Thread_base::utcb());
+			utcb_obj->crd_rcv = Obj_crd();
+			utcb_obj->crd_xlt = Obj_crd();
+
 			/* create SC */
 			unsigned sc_sel = cap_selector_allocator()->alloc();
 			res = create_sc(sc_sel, pd_sel, _tid.ec_sel, Qpd());
diff --git a/base-nova/src/core/thread_start.cc b/base-nova/src/core/thread_start.cc
index d4ae39724..68621a0df 100644
--- a/base-nova/src/core/thread_start.cc
+++ b/base-nova/src/core/thread_start.cc
@@ -77,9 +77,10 @@ void Thread_base::start()
 	 */
 	using namespace Nova;
 
-	addr_t sp   = reinterpret_cast<addr_t>(&_context->stack[-4]);
+	addr_t sp = reinterpret_cast<addr_t>(&_context->stack[-4]);
 	addr_t utcb = reinterpret_cast<addr_t>(&_context->utcb);
-	addr_t pd_sel   = Platform_pd::pd_core_sel();
+	Utcb * utcb_obj = reinterpret_cast<Utcb *>(&_context->utcb);
+	addr_t pd_sel = Platform_pd::pd_core_sel();
 
 	/* create local EC */
 	enum { CPU_NO = 0, GLOBAL = false };
@@ -90,6 +91,10 @@ void Thread_base::start()
 		throw Cpu_session::Thread_creation_failed();
 	}
 
+	/* default: we don't accept any mappings or translations */
+	utcb_obj->crd_rcv = Obj_crd();
+	utcb_obj->crd_xlt = Obj_crd();
+
 	if (map_local(reinterpret_cast<Nova::Utcb *>(Thread_base::myself()->utcb()),
 	              Obj_crd(PT_SEL_PAGE_FAULT, 0),
 	              Obj_crd(_tid.exc_pt_sel + PT_SEL_PAGE_FAULT, 0))) {