diff --git a/arangod/Aql/Types.cpp b/arangod/Aql/Types.cpp
index 634ffe3e59..30a1c9cef3 100644
--- a/arangod/Aql/Types.cpp
+++ b/arangod/Aql/Types.cpp
@@ -125,6 +125,18 @@ AqlItemBlock* AqlItemBlock::splice (std::vector<AqlItemBlock*>& blocks) {
   auto res = new AqlItemBlock(totalSize, nrRegs);
   size_t pos = 0;
   for (it = blocks.begin(); it != blocks.end(); ++it) {
+    if (it == blocks.begin()) {
+      for (RegisterId col = 0; col < nrRegs; ++col) {
+        res->getDocumentCollections().at(col)
+          = (*it)->getDocumentCollections().at(col);
+      }
+    }
+    else {
+      for (RegisterId col = 0; col < nrRegs; ++col) {
+        TRI_ASSERT(res->getDocumentCollections().at(col) ==
+                   (*it)->getDocumentCollections().at(col));
+      }
+    }
     for (size_t row = 0; row < (*it)->size(); ++row) {
       for (RegisterId col = 0; col < nrRegs; ++col) {
         res->setValue(pos+row, col, (*it)->getValue(row, col));
diff --git a/arangod/Aql/Types.h b/arangod/Aql/Types.h
index 6beb84961d..66377ae3ef 100644
--- a/arangod/Aql/Types.h
+++ b/arangod/Aql/Types.h
@@ -430,6 +430,9 @@ namespace triagens {
 
         std::unordered_map<AqlValue, AqlValue> cache;
         auto res = new AqlItemBlock(to - from, _nrRegs);
+        for (RegisterId col = 0; col < _nrRegs; col++) {
+          res->_docColls[col] = _docColls[col];
+        }
         for (size_t row = from; row < to; row++) {
           for (RegisterId col = 0; col < _nrRegs; col++) {
             AqlValue& a(_data[row * _nrRegs + col]);
@@ -459,6 +462,9 @@ namespace triagens {
 
         std::unordered_map<AqlValue, AqlValue> cache;
         auto res = new AqlItemBlock(to - from, _nrRegs);
+        for (RegisterId col = 0; col < _nrRegs; col++) {
+          res->_docColls[col] = _docColls[col];
+        }
         for (size_t row = from; row < to; row++) {
           for (RegisterId col = 0; col < _nrRegs; col++) {
             AqlValue& a(_data[chosen[row] * _nrRegs + col]);