diff --git a/arangod/VocBase/headers.cpp b/arangod/VocBase/headers.cpp
index 24595417a3..116fa137ac 100644
--- a/arangod/VocBase/headers.cpp
+++ b/arangod/VocBase/headers.cpp
@@ -210,18 +210,11 @@ static void UnlinkHeader (TRI_headers_t* h,
   if (headers->_nrLinked == 0) {
     TRI_ASSERT(headers->_begin == nullptr);
     TRI_ASSERT(headers->_end == nullptr);
-
-if (headers->_totalSize != 0) {
-  std::cout << "NONO HEADERS 1: " << headers->_totalSize << "\n";
-}
     TRI_ASSERT(headers->_totalSize == 0);
   }
   else {
     TRI_ASSERT(headers->_begin != nullptr);
     TRI_ASSERT(headers->_end != nullptr);
-if (headers->_totalSize <= 0) {
-  std::cout << "NONO HEADERS 2: " << headers->_totalSize << "\n";
-}
     TRI_ASSERT(headers->_totalSize > 0);
   }
   
diff --git a/arangod/VocBase/transaction.cpp b/arangod/VocBase/transaction.cpp
index f938efcc21..4b8a8cf1eb 100644
--- a/arangod/VocBase/transaction.cpp
+++ b/arangod/VocBase/transaction.cpp
@@ -858,7 +858,7 @@ int TRI_AddOperationTransaction (triagens::wal::DocumentOperation& operation,
     trx->_waitForSync = true;
   }
   
-  triagens::wal::SlotInfo slotInfo = triagens::wal::LogfileManager::instance()->allocateAndWrite(operation.marker->mem(), operation.marker->size(), waitForSync);
+  triagens::wal::StandaloneSlotInfo slotInfo = triagens::wal::LogfileManager::instance()->allocateAndWrite(operation.marker->mem(), operation.marker->size(), waitForSync);
   
   if (slotInfo.errorCode != TRI_ERROR_NO_ERROR) {
     // some error occurred
@@ -873,7 +873,9 @@ int TRI_AddOperationTransaction (triagens::wal::DocumentOperation& operation,
   }
 
   // set header file id
-  operation.header->_fid = slotInfo.slot->logfileId();
+  operation.header->_fid = slotInfo.logfileId;
+
+  TRI_ASSERT(operation.header->_fid > 0);
   
   TRI_document_collection_t* document = trxCollection->_collection->_collection;
   
diff --git a/arangod/VocBase/voc-shaper.cpp b/arangod/VocBase/voc-shaper.cpp
index 3538fce971..17ff3e5e68 100644
--- a/arangod/VocBase/voc-shaper.cpp
+++ b/arangod/VocBase/voc-shaper.cpp
@@ -192,7 +192,7 @@ static TRI_shape_aid_t FindOrCreateAttributeByName (TRI_shaper_t* shaper,
     }
 
     // write marker into wal
-    triagens::wal::SlotInfo slotInfo = triagens::wal::LogfileManager::instance()->allocateAndWrite(marker.mem(), marker.size(), false);
+    triagens::wal::StandaloneSlotInfo slotInfo = triagens::wal::LogfileManager::instance()->allocateAndWrite(marker.mem(), marker.size(), false);
 
     if (slotInfo.errorCode != TRI_ERROR_NO_ERROR) {
       LOG_WARNING("could not save attribute marker in log");
@@ -341,7 +341,7 @@ static TRI_shape_t const* FindShape (TRI_shaper_t* shaper,
     }
     
     // write marker into wal
-    triagens::wal::SlotInfo slotInfo = triagens::wal::LogfileManager::instance()->allocateAndWrite(marker.mem(), marker.size(), false);
+    triagens::wal::StandaloneSlotInfo slotInfo = triagens::wal::LogfileManager::instance()->allocateAndWrite(marker.mem(), marker.size(), false);
     
     if (slotInfo.errorCode != TRI_ERROR_NO_ERROR) {
       LOG_WARNING("could not save shape marker in log");
diff --git a/arangod/Wal/LogfileManager.cpp b/arangod/Wal/LogfileManager.cpp
index 6e907d8582..7f6c26c8d5 100644
--- a/arangod/Wal/LogfileManager.cpp
+++ b/arangod/Wal/LogfileManager.cpp
@@ -491,22 +491,25 @@ void LogfileManager::finalise (SlotInfo& slotInfo,
 /// this is a convenience function that combines allocate, memcpy and finalise
 ////////////////////////////////////////////////////////////////////////////////
 
-SlotInfo LogfileManager::allocateAndWrite (void* src,
-                                           uint32_t size,
-                                           bool waitForSync) {
+StandaloneSlotInfo LogfileManager::allocateAndWrite (void* src,
+                                                     uint32_t size,
+                                                     bool waitForSync) {
 
   SlotInfo slotInfo = allocate(size);
  
   if (slotInfo.errorCode != TRI_ERROR_NO_ERROR) {
-    return slotInfo;
+    return StandaloneSlotInfo(slotInfo.errorCode);
   }
 
   TRI_ASSERT(slotInfo.slot != nullptr);
 
   slotInfo.slot->fill(src, size);
+ 
+  // we must copy the slotinfo because finalise() will set its internal to 0 again
+  StandaloneSlotInfo copy(slotInfo.slot);
 
   finalise(slotInfo, waitForSync);
-  return slotInfo;
+  return copy;
 }
 
 ////////////////////////////////////////////////////////////////////////////////
diff --git a/arangod/Wal/LogfileManager.h b/arangod/Wal/LogfileManager.h
index ca5edc7018..df66ed2841 100644
--- a/arangod/Wal/LogfileManager.h
+++ b/arangod/Wal/LogfileManager.h
@@ -251,9 +251,9 @@ namespace triagens {
 /// this is a convenience function that combines allocate, memcpy and finalise
 ////////////////////////////////////////////////////////////////////////////////
 
-        SlotInfo allocateAndWrite (void*,
-                                   uint32_t,
-                                   bool);
+        StandaloneSlotInfo allocateAndWrite (void*,
+                                             uint32_t,
+                                             bool);
 
 ////////////////////////////////////////////////////////////////////////////////
 /// @brief re-inserts a logfile back into the inventory only
diff --git a/arangod/Wal/Slots.cpp b/arangod/Wal/Slots.cpp
index 922ffaebe0..587ff86824 100644
--- a/arangod/Wal/Slots.cpp
+++ b/arangod/Wal/Slots.cpp
@@ -195,6 +195,7 @@ SlotInfo Slots::nextUnused (uint32_t size) {
           return SlotInfo(TRI_ERROR_INTERNAL);
         }
 
+        // only in this case we return a valid slot
         slot->setUsed(static_cast<void*>(mem), size, _logfile->id(), handout());
 
         return SlotInfo(slot);
diff --git a/arangod/Wal/Slots.h b/arangod/Wal/Slots.h
index bce3ee6ad0..325be89690 100644
--- a/arangod/Wal/Slots.h
+++ b/arangod/Wal/Slots.h
@@ -40,6 +40,34 @@ namespace triagens {
 
     class LogfileManager;
 
+// -----------------------------------------------------------------------------
+// --SECTION--                                         struct StandaloneSlotInfo
+// -----------------------------------------------------------------------------
+    
+    struct StandaloneSlotInfo {
+      explicit StandaloneSlotInfo (Slot const* slot) 
+        : mem(slot->mem()),
+          size(slot->size()),
+          logfileId(slot->logfileId()),
+          tick(slot->tick()),
+          errorCode(TRI_ERROR_NO_ERROR) {
+      }
+
+      explicit StandaloneSlotInfo (int errorCode)
+        : mem(nullptr),
+          size(0),
+          logfileId(0),
+          tick(0),
+          errorCode(errorCode) {
+      }
+
+      void const*           mem;
+      uint32_t const        size;
+      Logfile::IdType const logfileId;
+      Slot::TickType const  tick;
+      int const             errorCode;
+    };
+
 // -----------------------------------------------------------------------------
 // --SECTION--                                                   struct SlotInfo
 // -----------------------------------------------------------------------------