diff --git a/base-nova/src/base/env/cap_sel_alloc.cc b/base-nova/src/base/env/cap_sel_alloc.cc
index 7048ddf48c..0d5f822c34 100644
--- a/base-nova/src/base/env/cap_sel_alloc.cc
+++ b/base-nova/src/base/env/cap_sel_alloc.cc
@@ -36,18 +36,15 @@ static Genode::Lock *alloc_lock()
 
 addr_t Cap_selector_allocator::alloc(size_t num_caps_log2)
 {
-	alloc_lock()->lock();
-	addr_t ret_base = Bit_allocator::alloc(num_caps_log2);
-	alloc_lock()->unlock();
-	return ret_base;
+	Lock::Guard(alloc_lock());
+	return Bit_allocator::alloc(num_caps_log2);
 }
 
 
 void Cap_selector_allocator::free(addr_t cap, size_t num_caps_log2)
 {
-	alloc_lock()->lock();
+	Lock::Guard(alloc_lock());
 	Bit_allocator::free(cap, num_caps_log2);
-	alloc_lock()->unlock();
 }