diff --git a/daemon/table/measurements.cpp b/daemon/table/measurements.cpp
index bc5a9d2..705d3f1 100644
--- a/daemon/table/measurements.cpp
+++ b/daemon/table/measurements.cpp
@@ -71,7 +71,7 @@
 //}
 
 void
-Measurements::extendLifetime(measurements::Entry& entry, time::Duration lifetime)
+Measurements::extendLifetime(measurements::Entry& entry, const time::Duration& lifetime)
 {
   std::map<Name, shared_ptr<measurements::Entry> >::iterator it =
       m_table.find(entry.getName());
@@ -83,7 +83,7 @@
 void
 Measurements::extendLifetimeInternal(
     std::map<Name, shared_ptr<measurements::Entry> >::iterator it,
-    time::Duration lifetime)
+    const time::Duration& lifetime)
 {
   shared_ptr<measurements::Entry>& entry = it->second;