diff --git a/src/openrct2/rct12/RCT12.cpp b/src/openrct2/rct12/RCT12.cpp
index d42fc3f6ba..4dde15bb62 100644
--- a/src/openrct2/rct12/RCT12.cpp
+++ b/src/openrct2/rct12/RCT12.cpp
@@ -1010,3 +1010,19 @@ bool RCT12ResearchItem::IsRandomEndMarker() const
 {
     return rawValue == RCT12_RESEARCHED_ITEMS_END_2;
 }
+
+ObjectEntryIndex RCTEntryIndexToOpenRCT2EntryIndex(RCT12ObjectEntryIndex index)
+{
+    if (index == RCT12_OBJECT_ENTRY_INDEX_NULL)
+        return OBJECT_ENTRY_INDEX_NULL;
+
+    return index;
+}
+
+RCT12ObjectEntryIndex OpenRCT2EntryIndexToRCTEntryIndex(ObjectEntryIndex index)
+{
+    if (index == OBJECT_ENTRY_INDEX_NULL)
+        return RCT12_OBJECT_ENTRY_INDEX_NULL;
+
+    return index;
+}
diff --git a/src/openrct2/rct12/RCT12.h b/src/openrct2/rct12/RCT12.h
index 014f336b89..a6c97bcb9e 100644
--- a/src/openrct2/rct12/RCT12.h
+++ b/src/openrct2/rct12/RCT12.h
@@ -12,6 +12,7 @@
 // Structures shared between both RCT1 and RCT2.
 
 #include "../common.h"
+#include "../object/Object.h"
 #include "../world/Location.hpp"
 
 #include <string>
@@ -49,7 +50,6 @@ constexpr uint16_t const RCT12_MAX_GOLF_HOLES = 31;
 constexpr uint16_t const RCT12_MAX_HELICES = 31;
 
 constexpr uint8_t RCT12_BANNER_INDEX_NULL = std::numeric_limits<uint8_t>::max();
-constexpr const uint8_t RCT12_OBJECT_ENTRY_INDEX_NULL = 255;
 
 constexpr const uint8_t RCT12_TILE_ELEMENT_SURFACE_EDGE_STYLE_MASK = 0xE0;   // in RCT12TileElement.properties.surface.slope
 constexpr const uint8_t RCT12_TILE_ELEMENT_SURFACE_WATER_HEIGHT_MASK = 0x1F; // in RCT12TileElement.properties.surface.terrain
@@ -792,3 +792,9 @@ struct RCT12ResearchItem
 assert_struct_size(RCT12ResearchItem, 5);
 
 #pragma pack(pop)
+
+using RCT12ObjectEntryIndex = uint8_t;
+constexpr const RCT12ObjectEntryIndex RCT12_OBJECT_ENTRY_INDEX_NULL = 255;
+
+ObjectEntryIndex RCTEntryIndexToOpenRCT2EntryIndex(RCT12ObjectEntryIndex index);
+RCT12ObjectEntryIndex OpenRCT2EntryIndexToRCTEntryIndex(ObjectEntryIndex index);