diff --git a/fairmq/shmem/UnmanagedRegion.h b/fairmq/shmem/UnmanagedRegion.h
index 7ecf5f29..9b81dba5 100644
--- a/fairmq/shmem/UnmanagedRegion.h
+++ b/fairmq/shmem/UnmanagedRegion.h
@@ -99,16 +99,25 @@ struct UnmanagedRegion
             fRegion = mapped_region(fFileMapping, read_write, 0, size, 0, cfg.creationFlags);
         } else {
             try {
-                fShmemObject = shared_memory_object(open_or_create, fName.c_str(), read_write);
-                if (size != 0) {
+                // if opening fails, create
+                try {
+                    fShmemObject = shared_memory_object(open_only, fName.c_str(), read_write);
+                } catch (interprocess_exception& e) {
+                    LOG(debug) << "Could not open " << (remote ? "remote" : "local") << " shared_memory_object for region id '" << cfg.id.value() << "': " << e.what() << ", creating...";
+                    fShmemObject = shared_memory_object(create_only, fName.c_str(), read_write);
                     fShmemObject.truncate(size);
                 }
             } catch (interprocess_exception& e) {
                 LOG(error) << "Failed " << (remote ? "opening" : "creating") << " shared_memory_object for region id '" << cfg.id.value() << "': " << e.what();
                 throw;
             }
+
             try {
                 fRegion = mapped_region(fShmemObject, read_write, 0, 0, 0, cfg.creationFlags);
+                if (size != 0 && size != fRegion.get_size()) {
+                    LOG(error) << "Created/opened region size (" << fRegion.get_size() << ") does not match configured size (" << size << ")";
+                    throw TransportError(tools::ToString("Created/opened region size (", fRegion.get_size(), ") does not match configured size (", size, ")"));
+                }
             } catch (interprocess_exception& e) {
                 LOG(error) << "Failed mapping shared_memory_object for region id '" << cfg.id.value() << "': " << e.what();
                 throw;
diff --git a/test/region/_region.cxx b/test/region/_region.cxx
index b6947e3f..c76eb1e3 100644
--- a/test/region/_region.cxx
+++ b/test/region/_region.cxx
@@ -25,6 +25,26 @@ namespace
 using namespace std;
 using namespace fair::mq;
 
+void RegionsSizeMismatch()
+{
+    size_t session = tools::UuidHash();
+
+    ProgOptions config;
+    config.SetProperty<string>("session", to_string(session));
+    config.SetProperty<size_t>("shm-segment-size", 100000000);
+
+    auto factory = TransportFactory::CreateTransportFactory("shmem", tools::Uuid(), &config);
+
+    fair::mq::RegionConfig rCfg;
+    rCfg.id = 10;
+    UnmanagedRegionPtr region1 = nullptr;
+    ASSERT_NO_THROW(region1 = factory->CreateUnmanagedRegion(10000, [](void*, size_t, void*) {}, rCfg));
+    ASSERT_NE(region1, nullptr);
+    UnmanagedRegionPtr region2 = nullptr;
+    ASSERT_THROW(region2 = factory->CreateUnmanagedRegion(16000, [](void*, size_t, void*) {}, rCfg), fair::mq::TransportError);
+    ASSERT_EQ(region2, nullptr);
+}
+
 void RegionsCache(const string& transport, const string& address)
 {
     size_t session1 = tools::UuidHash();
@@ -226,6 +246,11 @@ void RegionCallbacks(const string& transport, const string& _address)
     LOG(info) << "2 done.";
 }
 
+TEST(RegionsSizeMismatch, shmem)
+{
+    RegionsSizeMismatch();
+}
+
 TEST(Cache, zeromq)
 {
     RegionsCache("zeromq", "ipc://test_region_cache");