diff --git a/src/openrct2-ui/windows/NewRide.cpp b/src/openrct2-ui/windows/NewRide.cpp
index e6a9a0f672..33eab91ade 100644
--- a/src/openrct2-ui/windows/NewRide.cpp
+++ b/src/openrct2-ui/windows/NewRide.cpp
@@ -705,7 +705,7 @@ static void window_new_ride_mouseup(rct_window* w, rct_widgetindex widgetIndex)
             window_close(w);
             break;
         case WIDX_LAST_DEVELOPMENT_BUTTON:
-            news_item_open_subject(NEWS_ITEM_RESEARCH, gResearchLastItem.rawValue);
+            news_item_open_subject(NEWS_ITEM_RESEARCH, gResearchLastItem->rawValue);
             break;
         case WIDX_RESEARCH_FUNDING_BUTTON:
             context_open_window_view(WV_FINANCES_RESEARCH);
@@ -816,9 +816,9 @@ static void window_new_ride_invalidate(rct_window* w)
     if (_windowNewRideCurrentTab == WINDOW_NEW_RIDE_PAGE_RESEARCH)
     {
         window_new_ride_widgets[WIDX_LAST_DEVELOPMENT_BUTTON].type = WWT_EMPTY;
-        if (gResearchLastItem.rawValue != RESEARCHED_ITEMS_SEPARATOR)
+        if (gResearchLastItem.has_value())
         {
-            uint8_t type = gResearchLastItem.type;
+            uint8_t type = gResearchLastItem->type;
             window_new_ride_widgets[WIDX_LAST_DEVELOPMENT_BUTTON].type = WWT_FLATBTN;
             window_new_ride_widgets[WIDX_LAST_DEVELOPMENT_BUTTON].image = (type == RESEARCH_ENTRY_TYPE_RIDE) ? SPR_NEW_RIDE
                                                                                                              : SPR_NEW_SCENERY;
diff --git a/src/openrct2-ui/windows/Research.cpp b/src/openrct2-ui/windows/Research.cpp
index 0e991b20a3..524314e549 100644
--- a/src/openrct2-ui/windows/Research.cpp
+++ b/src/openrct2-ui/windows/Research.cpp
@@ -280,7 +280,7 @@ static void window_research_development_mouseup(rct_window* w, rct_widgetindex w
             window_research_set_page(w, widgetIndex - WIDX_TAB_1);
             break;
         case WIDX_LAST_DEVELOPMENT_BUTTON:
-            news_item_open_subject(NEWS_ITEM_RESEARCH, gResearchLastItem.rawValue);
+            news_item_open_subject(NEWS_ITEM_RESEARCH, gResearchLastItem->rawValue);
             break;
     }
 }
@@ -312,9 +312,9 @@ static void window_research_development_invalidate(rct_window* w)
     window_research_set_pressed_tab(w);
 
     window_research_development_widgets[WIDX_LAST_DEVELOPMENT_BUTTON].type = WWT_EMPTY;
-    if (gResearchLastItem.rawValue != RESEARCHED_ITEMS_SEPARATOR)
+    if (gResearchLastItem.has_value())
     {
-        uint8_t type = gResearchLastItem.type;
+        uint8_t type = gResearchLastItem->type;
         window_research_development_widgets[WIDX_LAST_DEVELOPMENT_BUTTON].type = WWT_FLATBTN;
         window_research_development_widgets[WIDX_LAST_DEVELOPMENT_BUTTON].image = type == RESEARCH_ENTRY_TYPE_RIDE
             ? SPR_NEW_RIDE
@@ -362,10 +362,10 @@ void window_research_development_page_paint(rct_window* w, rct_drawpixelinfo* dp
         stringId = STR_RESEARCH_UNKNOWN;
         if (gResearchProgressStage != RESEARCH_STAGE_INITIAL_RESEARCH)
         {
-            stringId = ResearchCategoryNames[gResearchNextItem.category];
+            stringId = ResearchCategoryNames[gResearchNextItem->category];
             if (gResearchProgressStage != RESEARCH_STAGE_DESIGNING)
             {
-                stringId = gResearchNextItem.GetName();
+                stringId = gResearchNextItem->GetName();
             }
         }
         gfx_draw_string_left_wrapped(dpi, &stringId, x, y, 296, STR_RESEARCH_TYPE_LABEL, COLOUR_BLACK);
@@ -397,10 +397,10 @@ void window_research_development_page_paint(rct_window* w, rct_drawpixelinfo* dp
     y = w->y + w->widgets[WIDX_LAST_DEVELOPMENT_GROUP + baseWidgetIndex].top + 12;
 
     rct_string_id lastDevelopmentFormat;
-    if (gResearchLastItem.rawValue != RESEARCHED_ITEMS_SEPARATOR)
+    if (gResearchLastItem.has_value())
     {
-        stringId = gResearchLastItem.GetName();
-        uint8_t type = gResearchLastItem.type;
+        stringId = gResearchLastItem->GetName();
+        uint8_t type = gResearchLastItem->type;
         lastDevelopmentFormat = (type == RESEARCH_ENTRY_TYPE_RIDE) ? STR_RESEARCH_RIDE_LABEL : STR_RESEARCH_SCENERY_LABEL;
 
         gfx_draw_string_left_wrapped(dpi, &stringId, x, y, 266, lastDevelopmentFormat, COLOUR_BLACK);
diff --git a/src/openrct2/management/Research.cpp b/src/openrct2/management/Research.cpp
index 8c97d8a708..0b0501ba7b 100644
--- a/src/openrct2/management/Research.cpp
+++ b/src/openrct2/management/Research.cpp
@@ -46,10 +46,10 @@ uint8_t gResearchFundingLevel;
 uint8_t gResearchPriorities;
 uint16_t gResearchProgress;
 uint8_t gResearchProgressStage;
-ResearchItem gResearchLastItem;
+std::optional<ResearchItem> gResearchLastItem;
 uint8_t gResearchExpectedMonth;
 uint8_t gResearchExpectedDay;
-ResearchItem gResearchNextItem;
+std::optional<ResearchItem> gResearchNextItem;
 
 // 0x01358844[500]
 ResearchItem gResearchItems[MAX_RESEARCH_ITEMS];
@@ -368,7 +368,7 @@ void research_update()
                 research_invalidate_related_windows();
                 break;
             case RESEARCH_STAGE_COMPLETING_DESIGN:
-                research_finish_item(&gResearchNextItem);
+                research_finish_item(&*gResearchNextItem);
                 gResearchProgress = 0;
                 gResearchProgressStage = RESEARCH_STAGE_INITIAL_RESEARCH;
                 research_calculate_expected_date();
@@ -400,7 +400,7 @@ void research_reset_current_item()
         research_finish_item(&researchItem);
     }
 
-    gResearchLastItem.rawValue = RESEARCHED_ITEMS_SEPARATOR;
+    gResearchLastItem = std::nullopt;
     gResearchProgressStage = RESEARCH_STAGE_INITIAL_RESEARCH;
     gResearchProgress = 0;
 }
diff --git a/src/openrct2/management/Research.h b/src/openrct2/management/Research.h
index 3459afa376..1b8d55adb4 100644
--- a/src/openrct2/management/Research.h
+++ b/src/openrct2/management/Research.h
@@ -10,6 +10,7 @@
 #pragma once
 
 #include "../common.h"
+#include "../core/Optional.hpp"
 #include "../object/ObjectLimits.h"
 #include "../ride/Ride.h"
 
@@ -99,8 +100,8 @@ extern uint16_t gResearchProgress;
 extern uint8_t gResearchProgressStage;
 extern uint8_t gResearchExpectedMonth;
 extern uint8_t gResearchExpectedDay;
-extern ResearchItem gResearchLastItem;
-extern ResearchItem gResearchNextItem;
+extern std::optional<ResearchItem> gResearchLastItem;
+extern std::optional<ResearchItem> gResearchNextItem;
 
 extern std::vector<ResearchItem> gResearchItemsUninvented;
 extern std::vector<ResearchItem> gResearchItemsInvented;
diff --git a/src/openrct2/rct1/S4Importer.cpp b/src/openrct2/rct1/S4Importer.cpp
index e1e8c79e30..a6cd533629 100644
--- a/src/openrct2/rct1/S4Importer.cpp
+++ b/src/openrct2/rct1/S4Importer.cpp
@@ -2388,13 +2388,29 @@ private:
         gResearchExpectedDay = _s4.next_research_expected_day;
         gResearchExpectedMonth = _s4.next_research_expected_month;
 
-        ConvertResearchEntry(&gResearchNextItem, _s4.next_research_item, _s4.next_research_type);
-        if (gResearchNextItem.IsInventedEndMarker())
+        if (_s4.last_research_flags == 0xFF)
         {
+            gResearchLastItem = std::nullopt;
+        }
+        else
+        {
+            ResearchItem researchItem = {};
+            ConvertResearchEntry(&researchItem, _s4.last_research_item, _s4.last_research_type);
+            gResearchLastItem = researchItem;
+        }
+
+        if (_s4.next_research_flags == 0xFF)
+        {
+            gResearchNextItem = std::nullopt;
             gResearchProgressStage = RESEARCH_STAGE_INITIAL_RESEARCH;
             gResearchProgress = 0;
         }
-        ConvertResearchEntry(&gResearchLastItem, _s4.last_research_item, _s4.last_research_type);
+        else
+        {
+            ResearchItem researchItem = {};
+            ConvertResearchEntry(&researchItem, _s4.next_research_item, _s4.next_research_type);
+            gResearchNextItem = researchItem;
+        }
     }
 
     static std::bitset<RCT1_RIDE_TYPE_COUNT> GetRideTypesPresentInResearchList(
diff --git a/src/openrct2/rct2/S6Exporter.cpp b/src/openrct2/rct2/S6Exporter.cpp
index 5567f98043..942e7c7816 100644
--- a/src/openrct2/rct2/S6Exporter.cpp
+++ b/src/openrct2/rct2/S6Exporter.cpp
@@ -241,11 +241,24 @@ void S6Exporter::Export()
 
     _s6.active_research_types = gResearchPriorities;
     _s6.research_progress_stage = gResearchProgressStage;
-    _s6.last_researched_item_subject = gResearchLastItem.rawValue;
+    if (gResearchLastItem.has_value())
+        _s6.last_researched_item_subject = gResearchLastItem->rawValue;
+    else
+        _s6.last_researched_item_subject = -1;
     // pad_01357CF8
-    _s6.next_research_item = gResearchNextItem.rawValue;
     _s6.research_progress = gResearchProgress;
-    _s6.next_research_category = gResearchNextItem.category;
+
+    if (gResearchNextItem.has_value())
+    {
+        _s6.next_research_item = gResearchNextItem->rawValue;
+        _s6.next_research_category = gResearchNextItem->category;
+    }
+    else
+    {
+        _s6.next_research_item = -1;
+        _s6.next_research_category = 0;
+    }
+
     _s6.next_research_expected_day = gResearchExpectedDay;
     _s6.next_research_expected_month = gResearchExpectedMonth;
     _s6.guest_initial_happiness = gGuestInitialHappiness;
diff --git a/src/openrct2/rct2/S6Importer.cpp b/src/openrct2/rct2/S6Importer.cpp
index 71b659f886..e64ce58500 100644
--- a/src/openrct2/rct2/S6Importer.cpp
+++ b/src/openrct2/rct2/S6Importer.cpp
@@ -262,11 +262,18 @@ public:
 
         gResearchPriorities = _s6.active_research_types;
         gResearchProgressStage = _s6.research_progress_stage;
-        gResearchLastItem.rawValue = _s6.last_researched_item_subject;
+        if (_s6.last_researched_item_subject != RCT12_RESEARCHED_ITEMS_SEPARATOR)
+            gResearchLastItem = std::make_optional(
+                ResearchItem{ _s6.last_researched_item_subject, RESEARCH_CATEGORY_TRANSPORT });
+        else
+            gResearchLastItem = std::nullopt;
         // pad_01357CF8
-        gResearchNextItem.rawValue = _s6.next_research_item;
+        if (_s6.next_research_item != RCT12_RESEARCHED_ITEMS_SEPARATOR)
+            gResearchNextItem = std::make_optional(ResearchItem{ _s6.next_research_item, _s6.next_research_category });
+        else
+            gResearchNextItem = std::nullopt;
+
         gResearchProgress = _s6.research_progress;
-        gResearchNextItem.category = _s6.next_research_category;
         gResearchExpectedDay = _s6.next_research_expected_day;
         gResearchExpectedMonth = _s6.next_research_expected_month;
         gGuestInitialHappiness = _s6.guest_initial_happiness;
diff --git a/src/openrct2/scenario/Scenario.h b/src/openrct2/scenario/Scenario.h
index 56e06876e0..ee3d2f7e84 100644
--- a/src/openrct2/scenario/Scenario.h
+++ b/src/openrct2/scenario/Scenario.h
@@ -162,9 +162,9 @@ struct rct_s6_data
     // SC6[10]
     uint8_t active_research_types;
     uint8_t research_progress_stage;
-    uint32_t last_researched_item_subject;
+    int32_t last_researched_item_subject;
     uint8_t pad_01357CF8[1000];
-    uint32_t next_research_item;
+    int32_t next_research_item;
     uint16_t research_progress;
     uint8_t next_research_category;
     uint8_t next_research_expected_day;
diff --git a/src/openrct2/world/Park.cpp b/src/openrct2/world/Park.cpp
index 6d342f2804..e11bb9ff16 100644
--- a/src/openrct2/world/Park.cpp
+++ b/src/openrct2/world/Park.cpp
@@ -268,7 +268,7 @@ void Park::Initialise()
     gParkRating = 0;
     _guestGenerationProbability = 0;
     gTotalRideValueForMoney = 0;
-    gResearchLastItem.rawValue = RESEARCHED_ITEMS_SEPARATOR;
+    gResearchLastItem = std::nullopt;
     gMarketingCampaigns.clear();
 
     research_reset_items();