diff --git a/src/messages/MMonPaxos.h b/src/messages/MMonPaxos.h
index 309246add39..f63684144b0 100644
--- a/src/messages/MMonPaxos.h
+++ b/src/messages/MMonPaxos.h
@@ -51,7 +51,7 @@ class MMonPaxos : public Message {
   version_t pn_from;         // i promise to accept after
   version_t pn;              // with with proposal
   version_t uncommitted_pn;     // previous pn, if we are a LAST with an uncommitted value
-  utime_t lease_expire;
+  utime_t lease_timestamp;
 
   version_t latest_version;
   bufferlist latest_value;
@@ -92,7 +92,7 @@ public:
     ::encode(pn_from, payload);
     ::encode(pn, payload);
     ::encode(uncommitted_pn, payload);
-    ::encode(lease_expire, payload);
+    ::encode(lease_timestamp, payload);
     ::encode(latest_version, payload);
     ::encode(latest_value, payload);
     ::encode(values, payload);
@@ -107,7 +107,7 @@ public:
     ::decode(pn_from, p);   
     ::decode(pn, p);   
     ::decode(uncommitted_pn, p);
-    ::decode(lease_expire, p);
+    ::decode(lease_timestamp, p);
     ::decode(latest_version, p);
     ::decode(latest_value, p);
     ::decode(values, p);
diff --git a/src/mon/Paxos.cc b/src/mon/Paxos.cc
index c3be917b418..9cad6d6de9a 100644
--- a/src/mon/Paxos.cc
+++ b/src/mon/Paxos.cc
@@ -536,7 +536,7 @@ void Paxos::extend_lease()
     if (*p == whoami) continue;
     MMonPaxos *lease = new MMonPaxos(mon->get_epoch(), MMonPaxos::OP_LEASE, machine_id);
     lease->last_committed = last_committed;
-    lease->lease_expire = lease_expire;
+    lease->lease_timestamp = lease_expire;
     lease->first_committed = first_committed;
     mon->messenger->send_message(lease, mon->monmap->get_inst(*p));
   }
@@ -569,8 +569,15 @@ void Paxos::handle_lease(MMonPaxos *lease)
   }
 
   // extend lease
-  if (lease_expire < lease->lease_expire) 
-    lease_expire = lease->lease_expire;
+  if (lease_expire < lease->lease_timestamp) {
+    lease_expire = lease->lease_timestamp;
+    if (g_clock.now() > lease_expire) {
+      dout(0) << "lease_expire " << lease_expire
+	      << " is in the past (current time " << g_clock.now()
+	      << "). Clocks not synchronized or connection is very laggy"
+	      << dendl;
+    }
+  }
   
   state = STATE_ACTIVE;
   
@@ -581,7 +588,7 @@ void Paxos::handle_lease(MMonPaxos *lease)
   MMonPaxos *ack = new MMonPaxos(mon->get_epoch(), MMonPaxos::OP_LEASE_ACK, machine_id);
   ack->last_committed = last_committed;
   ack->first_committed = first_committed;
-  ack->lease_expire = lease_expire;
+  ack->lease_timestamp = g_clock.now();
   mon->messenger->send_message(ack, lease->get_source_inst());
 
   // (re)set timeout event.
@@ -627,6 +634,15 @@ void Paxos::handle_lease_ack(MMonPaxos *ack)
     dout(10) << "handle_lease_ack from " << ack->get_source() 
 	     << " dup (lagging!), ignoring" << dendl;
   }
+  if (ack->lease_timestamp > g_clock.now())
+    dout(0) << "lease_ack from follower mon" << from
+	    << " was sent from future time " << ack->lease_timestamp
+	    << "! Clocks not synchronized." << dendl;
+  if (ack->lease_timestamp < (lease_expire - g_conf.mon_lease))
+    dout(0) << "lease_ack from follower sent at time("
+	    << ack->lease_timestamp << "), before lease extend was sent ("
+	    << lease_expire - g_conf.mon_lease
+	    << ")! Clocks not synchronized." << dendl;
   
   ack->put();
 }