diff --git a/fairmq/shmem/Manager.h b/fairmq/shmem/Manager.h
index ba90ca14..ee87e73e 100644
--- a/fairmq/shmem/Manager.h
+++ b/fairmq/shmem/Manager.h
@@ -396,7 +396,23 @@ class Manager
                 const uint16_t id = cfg.id.value();
 
                 std::lock_guard<std::mutex> lock(fLocalRegionsMtx);
-                auto& region = fRegions[id] = std::make_unique<UnmanagedRegion>(fShmId, size, true, cfg);
+
+                UnmanagedRegion* region = nullptr;
+
+                auto it = fRegions.find(id);
+                if (it != fRegions.end()) {
+                    region = it->second.get();
+                    if (region->fControlling) {
+                        LOG(error) << "Unmanaged Region with id " << id << " already exists. Only unique IDs per session are allowed.";
+                        throw TransportError(tools::ToString("Unmanaged Region with id ", id, " already exists. Only unique IDs per session are allowed."));
+                    }
+
+                    LOG(debug) << "Unmanaged region (view) already present, promoting to controller";
+                    region->BecomeController(cfg);
+                } else {
+                    auto res = fRegions.emplace(id, std::make_unique<UnmanagedRegion>(fShmId, size, true, cfg));
+                    region = res.first->second.get();
+                }
                 // LOG(debug) << "Created region with id '" << id << "', path: '" << cfg.path << "', flags: '" << cfg.creationFlags << "'";
 
                 // start ack receiver only if a callback has been provided.
@@ -406,7 +422,7 @@ class Manager
                     region->StartAckSender();
                     region->StartAckReceiver();
                 }
-                result.first = region.get();
+                result.first = region;
                 result.second = id;
             }
             fRegionsGen += 1; // signal TL cache invalidation
diff --git a/fairmq/shmem/UnmanagedRegion.h b/fairmq/shmem/UnmanagedRegion.h
index 2981cf39..18edcfa7 100644
--- a/fairmq/shmem/UnmanagedRegion.h
+++ b/fairmq/shmem/UnmanagedRegion.h
@@ -146,7 +146,7 @@ struct UnmanagedRegion
             LOG(debug) << "Successfully zeroed free memory of region " << id << ".";
         }
 
-        if (fControlling) {
+        if (fControlling && created) {
             Register(shmId, cfg);
         }
 
@@ -160,6 +160,13 @@ struct UnmanagedRegion
     UnmanagedRegion& operator=(const UnmanagedRegion&) = delete;
     UnmanagedRegion& operator=(UnmanagedRegion&&) = delete;
 
+    void BecomeController(RegionConfig& cfg)
+    {
+        fControlling = true;
+        fLinger = cfg.linger;
+        fRemoveOnDestruction = cfg.removeOnDestruction;
+    }
+
     void Zero()
     {
         memset(fRegion.get_address(), 0x00, fRegion.get_size());
@@ -263,10 +270,14 @@ struct UnmanagedRegion
 
         EventCounter* eventCounter = mngSegment.find_or_construct<EventCounter>(unique_instance)(0);
 
-        bool newShmRegionCreated = shmRegions->emplace(cfg.id.value(), RegionInfo(cfg.path.c_str(), cfg.creationFlags, cfg.userFlags, cfg.size, alloc)).second;
-        if (newShmRegionCreated) {
-            (eventCounter->fCount)++;
+        auto it = shmRegions->find(cfg.id.value());
+        if (it != shmRegions->end()) {
+            LOG(error) << "Unmanaged Region with id " << cfg.id.value() << " has already been registered. Only unique IDs per session are allowed.";
+            throw TransportError(tools::ToString("Unmanaged Region with id ", cfg.id.value(), " has already been registered. Only unique IDs per session are allowed."));
         }
+
+        shmRegions->emplace(cfg.id.value(), RegionInfo(cfg.path.c_str(), cfg.creationFlags, cfg.userFlags, cfg.size, alloc)).second;
+        (eventCounter->fCount)++;
     }
 
     void SetCallbacks(RegionCallback callback, RegionBulkCallback bulkCallback)