diff --git a/src/openrct2/management/Research.cpp b/src/openrct2/management/Research.cpp
index 13e5f6240e..18d8698ba1 100644
--- a/src/openrct2/management/Research.cpp
+++ b/src/openrct2/management/Research.cpp
@@ -669,8 +669,9 @@ void research_insert_scenery_group_entry(uint8 entryIndex, bool researched)
     research_insert(researched, entryIndex, RESEARCH_CATEGORY_SCENERY_GROUP);
 }
 
-bool ride_type_is_invented(sint32 rideType)
+bool ride_type_is_invented(uint32 rideType)
 {
+    Guard::Assert(rideType < Util::CountOf(_researchedRideTypes), GUARD_LINE);
     return _researchedRideTypes[rideType];
 }
 
@@ -684,8 +685,9 @@ bool track_piece_is_available_for_ride_type(uint8 rideType, sint32 trackType)
     return RideTypePossibleTrackConfigurations[rideType] & (1ULL << trackType);
 }
 
-void ride_type_set_invented(sint32 rideType)
+void ride_type_set_invented(uint32 rideType)
 {
+    Guard::Assert(rideType < Util::CountOf(_researchedRideTypes), GUARD_LINE);
     _researchedRideTypes[rideType] = true;
 }
 
diff --git a/src/openrct2/management/Research.h b/src/openrct2/management/Research.h
index 50991f8b77..188b3ddcfe 100644
--- a/src/openrct2/management/Research.h
+++ b/src/openrct2/management/Research.h
@@ -125,11 +125,11 @@ void research_remove(rct_research_item * researchItem);
 void research_insert_ride_entry(uint8 entryIndex, bool researched);
 void research_insert_scenery_group_entry(uint8 entryIndex, bool researched);
 
-void ride_type_set_invented(sint32 rideType);
+void ride_type_set_invented(uint32 rideType);
 void ride_entry_set_invented(sint32 rideEntryIndex);
 void scenery_set_invented(uint16 sceneryItem);
 void scenery_set_not_invented(uint16 sceneryItem);
-bool ride_type_is_invented(sint32 rideType);
+bool ride_type_is_invented(uint32 rideType);
 bool ride_entry_is_invented(sint32 rideEntryIndex);
 bool track_piece_is_available_for_ride_type(uint8 rideType, sint32 trackType);
 bool scenery_group_is_invented(sint32 sgIndex);
diff --git a/src/openrct2/peep/Peep.cpp b/src/openrct2/peep/Peep.cpp
index 9a2763b525..fb74b13bac 100644
--- a/src/openrct2/peep/Peep.cpp
+++ b/src/openrct2/peep/Peep.cpp
@@ -3622,6 +3622,7 @@ static void peep_update_ride_prepare_for_state_9(rct_peep * peep)
 {
     Ride * ride = get_ride(peep->current_ride);
 
+    Guard::Assert(peep->current_ride_station < Util::CountOf(ride->exits), GUARD_LINE);
     sint16 x = ride->exits[peep->current_ride_station].x;
     sint16 y = ride->exits[peep->current_ride_station].y;
     sint16 z = ride->station_heights[peep->current_ride_station];