diff --git a/apps/opencs/model/world/refcollection.cpp b/apps/opencs/model/world/refcollection.cpp
index 124e697de8..5d2ed2cfc5 100644
--- a/apps/opencs/model/world/refcollection.cpp
+++ b/apps/opencs/model/world/refcollection.cpp
@@ -175,6 +175,9 @@ void CSMWorld::RefCollection::load(ESM::ESMReader& reader, int cellIndex, bool b
             ref.mIdNum = mNextId; // FIXME: fragile
             ref.mId = ESM::RefId::stringRefId(getNewId());
 
+            if (!base && ref.mRefNum.mIndex >= mHighestUsedRefNum)
+                mHighestUsedRefNum = ref.mRefNum.mIndex;
+
             cache.emplace(ref.mRefNum, ref.mIdNum);
 
             auto record = std::make_unique<Record<CellRef>>();
@@ -222,6 +225,11 @@ std::string CSMWorld::RefCollection::getNewId()
     return "ref#" + std::to_string(mNextId++);
 }
 
+uint32_t CSMWorld::RefCollection::getNextRefNum()
+{
+    return ++mHighestUsedRefNum;
+}
+
 unsigned int CSMWorld::RefCollection::extractIdNum(std::string_view id) const
 {
     std::string::size_type separator = id.find_last_of('#');
@@ -283,6 +291,7 @@ void CSMWorld::RefCollection::appendBlankRecord(const ESM::RefId& id, UniversalI
 
     record->get().mId = id;
     record->get().mIdNum = extractIdNum(id.getRefIdString());
+    record->get().mRefNum.mIndex = getNextRefNum();
 
     Collection<CellRef>::appendRecord(std::move(record));
 }
@@ -298,15 +307,13 @@ void CSMWorld::RefCollection::cloneRecord(
 
     copy->get().mId = destination;
     copy->get().mIdNum = extractIdNum(destination.getRefIdString());
+    copy->get().mRefNum.mIndex = getNextRefNum();
 
     if (copy->get().mRefNum.hasContentFile())
     {
         mRefIndex.insert(std::make_pair(static_cast<Record<CellRef>*>(copy.get())->get().mIdNum, index));
         copy->get().mRefNum.mContentFile = -1;
-        copy->get().mRefNum.mIndex = index;
     }
-    else
-        copy->get().mRefNum.mIndex = copy->get().mIdNum;
 
     insertRecord(std::move(copy), getAppendIndex(destination, type)); // call RefCollection::insertRecord()
 }
diff --git a/apps/opencs/model/world/refcollection.hpp b/apps/opencs/model/world/refcollection.hpp
index d3d200e6c2..f70167f922 100644
--- a/apps/opencs/model/world/refcollection.hpp
+++ b/apps/opencs/model/world/refcollection.hpp
@@ -1,6 +1,7 @@
 #ifndef CSM_WOLRD_REFCOLLECTION_H
 #define CSM_WOLRD_REFCOLLECTION_H
 
+#include <cstdint>
 #include <map>
 #include <memory>
 #include <string>
@@ -40,9 +41,12 @@ namespace CSMWorld
         std::map<unsigned int, int> mRefIndex; // CellRef index keyed by CSMWorld::CellRef::mIdNum
 
         int mNextId;
+        uint32_t mHighestUsedRefNum = 0;
 
         unsigned int extractIdNum(std::string_view id) const;
 
+        uint32_t getNextRefNum();
+
         int getIntIndex(unsigned int id) const;
 
         int searchId(unsigned int id) const;