diff --git a/fairmq/shmem/Common.h b/fairmq/shmem/Common.h
index a2f9acf5..3da2e605 100644
--- a/fairmq/shmem/Common.h
+++ b/fairmq/shmem/Common.h
@@ -58,19 +58,22 @@ struct RegionInfo
         : fPath("", alloc)
         , fCreationFlags(0)
         , fUserFlags(0)
+        , fSize(0)
         , fDestroyed(false)
     {}
 
-    RegionInfo(const char* path, const int flags, const uint64_t userFlags, const VoidAlloc& alloc)
+    RegionInfo(const char* path, int flags, uint64_t userFlags, uint64_t size, const VoidAlloc& alloc)
         : fPath(path, alloc)
         , fCreationFlags(flags)
         , fUserFlags(userFlags)
+        , fSize(size)
         , fDestroyed(false)
     {}
 
     Str fPath;
     int fCreationFlags;
     uint64_t fUserFlags;
+    uint64_t fSize;
     bool fDestroyed;
 };
 
diff --git a/fairmq/shmem/Monitor.cxx b/fairmq/shmem/Monitor.cxx
index 4e97db4c..38ad76e3 100644
--- a/fairmq/shmem/Monitor.cxx
+++ b/fairmq/shmem/Monitor.cxx
@@ -267,6 +267,7 @@ bool Monitor::PrintShm(const ShmId& shmId)
             ss << "\n   unmanaged regions:";
             for (const auto& r : *shmRegions) {
                 ss << "\n      [" << r.first << "]: " << (r.second.fDestroyed ? "destroyed" : "alive");
+                ss << ", size: " << r.second.fSize;
 
                 try {
                     boost::interprocess::message_queue q(open_only, std::string("fmq_" + std::string(shmId) + "_rgq_" + to_string(r.first)).c_str());
diff --git a/fairmq/shmem/UnmanagedRegion.h b/fairmq/shmem/UnmanagedRegion.h
index 592b4d36..651630ec 100644
--- a/fairmq/shmem/UnmanagedRegion.h
+++ b/fairmq/shmem/UnmanagedRegion.h
@@ -119,7 +119,7 @@ struct UnmanagedRegion
         }
 
         if (!remote) {
-            Register(shmId, cfg);
+            Register(shmId, cfg, size);
         }
 
         LOG(trace) << "shmem: initialized region: " << fName << " (" << (remote ? "remote" : "local") << ")";
@@ -223,7 +223,7 @@ struct UnmanagedRegion
         return regionCfg;
     }
 
-    static void Register(const std::string& shmId, RegionConfig& cfg)
+    static void Register(const std::string& shmId, RegionConfig& cfg, uint64_t size)
     {
         using namespace boost::interprocess;
         managed_shared_memory mngSegment(open_or_create, std::string("fmq_" + shmId + "_mng").c_str(), 6553600);
@@ -236,7 +236,7 @@ struct UnmanagedRegion
             eventCounter = mngSegment.construct<EventCounter>(unique_instance)(0);
         }
 
-        bool newShmRegionCreated = shmRegions->emplace(cfg.id.value(), RegionInfo(cfg.path.c_str(), cfg.creationFlags, cfg.userFlags, alloc)).second;
+        bool newShmRegionCreated = shmRegions->emplace(cfg.id.value(), RegionInfo(cfg.path.c_str(), cfg.creationFlags, cfg.userFlags, size, alloc)).second;
         if (newShmRegionCreated) {
             (eventCounter->fCount)++;
         }