diff --git a/src/Synchronizer.cpp b/src/Synchronizer.cpp
index 8f59302b7..99021821b 100644
--- a/src/Synchronizer.cpp
+++ b/src/Synchronizer.cpp
@@ -150,8 +150,10 @@ void Synchronizer::flushObject(const string &key)
     {
         auto op = opsInProgress.find(key);
         // it's already in progress
-        if (op != opsInProgress.end())
-            op->second->wait(&mutex);
+        if (op != opsInProgress.end()) {
+            boost::shared_ptr<PendingOps> tmp = op->second;
+            tmp->wait(&mutex);
+        }
         else
         {
             // it's not in either one, trigger existence check
@@ -237,7 +239,8 @@ void Synchronizer::process(list<string>::iterator name)
         // it's already in progress
         if (op != opsInProgress.end())
         {
-            op->second->wait(&mutex);
+            boost::shared_ptr<PendingOps> tmp = op->second;
+            tmp->wait(&mutex);
             return;
         }
         else
@@ -246,9 +249,12 @@ void Synchronizer::process(list<string>::iterator name)
     }
     
     boost::shared_ptr<PendingOps> pending = it->second;
-    opsInProgress[key] = pending;
-    pendingOps.erase(it);
+    bool inserted = opsInProgress.insert(*it).second;
+    if (!inserted)
+        return;    // the one in pending will have to wait until the next time to avoid clobbering waiting threads
+    //opsInProgress[key] = it->second;
     string sourceFile = MetadataFile::getSourceFromKey(*name);
+    pendingOps.erase(it);
     s.unlock();
     
     bool success = false;
@@ -271,11 +277,12 @@ void Synchronizer::process(list<string>::iterator name)
                 synchronize(sourceFile, name);
             else
                 throw logic_error("Synchronizer::process(): got an unknown op flag");
-            pending->notify(&mutex);
+            s.lock();
+            pending->notify();
             success = true;
         }
         catch(exception &e) {
-            logger->log(LOG_CRIT, "Synchronizer::process(): error sync'ing %s opFlags=%d, got '%s'.  Requeueing...", key.c_str(),
+            logger->log(LOG_CRIT, "Synchronizer::process(): error sync'ing %s opFlags=%d, got '%s'.  Retrying...", key.c_str(),
                 pending->opFlags, e.what());
             success = false;
             sleep(1);
@@ -295,8 +302,6 @@ void Synchronizer::process(list<string>::iterator name)
             return;
         }
     }
-    
-    s.lock();
         
     opsInProgress.erase(key);
     objNames.erase(name);
@@ -503,13 +508,17 @@ bf::path Synchronizer::getCachePath()
 
 /* The helper objects & fcns */
 
-Synchronizer::PendingOps::PendingOps(int flags) : opFlags(flags), finished(false)
+Synchronizer::PendingOps::PendingOps(int flags) : opFlags(flags), waiters(0), finished(false)
 {
 }
 
-void Synchronizer::PendingOps::notify(boost::recursive_mutex *m)
+Synchronizer::PendingOps::~PendingOps()
+{
+    assert(waiters == 0);
+}
+
+void Synchronizer::PendingOps::notify()
 {
-    boost::unique_lock<boost::recursive_mutex> s(*m);
     finished = true;
     condvar.notify_all();
 }
@@ -517,7 +526,11 @@ void Synchronizer::PendingOps::notify(boost::recursive_mutex *m)
 void Synchronizer::PendingOps::wait(boost::recursive_mutex *m)
 {
     while (!finished)
+    {
+        waiters++;
         condvar.wait(*m);
+        waiters--;
+    }
 }
 
 }
diff --git a/src/Synchronizer.h b/src/Synchronizer.h
index 036d19512..2b8d0994a 100644
--- a/src/Synchronizer.h
+++ b/src/Synchronizer.h
@@ -51,11 +51,13 @@ class Synchronizer : public boost::noncopyable
         struct PendingOps
         {
             PendingOps(int flags);
+            ~PendingOps();
             int opFlags;
+            int waiters;
             bool finished;
             boost::condition condvar;
             void wait(boost::recursive_mutex *);
-            void notify(boost::recursive_mutex *);
+            void notify();
         };
         
         struct Job : public ThreadPool::Job