diff --git a/src/openrct2/actions/GameAction.cpp b/src/openrct2/actions/GameAction.cpp
index 51c3175228..2b0bc1e174 100644
--- a/src/openrct2/actions/GameAction.cpp
+++ b/src/openrct2/actions/GameAction.cpp
@@ -475,7 +475,8 @@ namespace GameActions
                     NetworkPlayerId_t playerId = action->GetPlayer();
 
                     int32_t playerIndex = network_get_player_index(playerId.id);
-                    Guard::Assert(playerIndex != -1);
+                    Guard::Assert(
+                        playerIndex != -1, "Unable to find player %u for game action %u", playerId, action->GetType());
 
                     network_set_player_last_action(playerIndex, action->GetType());
                     if (result->Cost != 0)
diff --git a/src/openrct2/core/Guard.hpp b/src/openrct2/core/Guard.hpp
index a41572cf1a..7b72aa068b 100644
--- a/src/openrct2/core/Guard.hpp
+++ b/src/openrct2/core/Guard.hpp
@@ -68,6 +68,12 @@ namespace Guard
         Assert(argument >= min && argument <= max, message, args);
         va_end(args);
     }
+
+    template<typename T> static void IndexInRange(size_t index, const T& container)
+    {
+        Guard::Assert(index >= container.size(), "Index %zu out of bounds (%zu)", index, container.size());
+    }
+
 } // namespace Guard
 
 #define GUARD_LINE "Location: %s:%d", __func__, __LINE__
diff --git a/src/openrct2/network/NetworkBase.cpp b/src/openrct2/network/NetworkBase.cpp
index 5ad0703477..5f6889a955 100644
--- a/src/openrct2/network/NetworkBase.cpp
+++ b/src/openrct2/network/NetworkBase.cpp
@@ -3329,26 +3329,36 @@ int32_t network_get_num_players()
 
 const char* network_get_player_name(uint32_t index)
 {
+    Guard::IndexInRange(index, gNetwork.player_list);
+
     return static_cast<const char*>(gNetwork.player_list[index]->Name.c_str());
 }
 
 uint32_t network_get_player_flags(uint32_t index)
 {
+    Guard::IndexInRange(index, gNetwork.player_list);
+
     return gNetwork.player_list[index]->Flags;
 }
 
 int32_t network_get_player_ping(uint32_t index)
 {
+    Guard::IndexInRange(index, gNetwork.player_list);
+
     return gNetwork.player_list[index]->Ping;
 }
 
 int32_t network_get_player_id(uint32_t index)
 {
+    Guard::IndexInRange(index, gNetwork.player_list);
+
     return gNetwork.player_list[index]->Id;
 }
 
 money32 network_get_player_money_spent(uint32_t index)
 {
+    Guard::IndexInRange(index, gNetwork.player_list);
+
     return gNetwork.player_list[index]->MoneySpent;
 }
 
@@ -3374,11 +3384,15 @@ std::string network_get_player_public_key_hash(uint32_t id)
 
 void network_add_player_money_spent(uint32_t index, money32 cost)
 {
+    Guard::IndexInRange(index, gNetwork.player_list);
+
     gNetwork.player_list[index]->AddMoneySpent(cost);
 }
 
 int32_t network_get_player_last_action(uint32_t index, int32_t time)
 {
+    Guard::IndexInRange(index, gNetwork.player_list);
+
     if (time && platform_get_ticks() > gNetwork.player_list[index]->LastActionTime + time)
     {
         return -999;
@@ -3388,17 +3402,23 @@ int32_t network_get_player_last_action(uint32_t index, int32_t time)
 
 void network_set_player_last_action(uint32_t index, int32_t command)
 {
+    Guard::IndexInRange(index, gNetwork.player_list);
+
     gNetwork.player_list[index]->LastAction = NetworkActions::FindCommand(command);
     gNetwork.player_list[index]->LastActionTime = platform_get_ticks();
 }
 
 CoordsXYZ network_get_player_last_action_coord(uint32_t index)
 {
+    Guard::IndexInRange(index, gNetwork.player_list);
+
     return gNetwork.player_list[index]->LastActionCoord;
 }
 
 void network_set_player_last_action_coord(uint32_t index, const CoordsXYZ& coord)
 {
+    Guard::IndexInRange(index, gNetwork.player_list);
+
     if (index < gNetwork.player_list.size())
     {
         gNetwork.player_list[index]->LastActionCoord = coord;
@@ -3407,6 +3427,8 @@ void network_set_player_last_action_coord(uint32_t index, const CoordsXYZ& coord
 
 uint32_t network_get_player_commands_ran(uint32_t index)
 {
+    Guard::IndexInRange(index, gNetwork.player_list);
+
     return gNetwork.player_list[index]->CommandsRan;
 }
 
@@ -3422,11 +3444,16 @@ int32_t network_get_player_index(uint32_t id)
 
 uint8_t network_get_player_group(uint32_t index)
 {
+    Guard::IndexInRange(index, gNetwork.player_list);
+
     return gNetwork.player_list[index]->Group;
 }
 
 void network_set_player_group(uint32_t index, uint32_t groupindex)
 {
+    Guard::IndexInRange(index, gNetwork.player_list);
+    Guard::IndexInRange(groupindex, gNetwork.group_list);
+
     gNetwork.player_list[index]->Group = gNetwork.group_list[groupindex]->Id;
 }
 
@@ -3442,6 +3469,8 @@ int32_t network_get_group_index(uint8_t id)
 
 uint8_t network_get_group_id(uint32_t index)
 {
+    Guard::IndexInRange(index, gNetwork.group_list);
+
     return gNetwork.group_list[index]->Id;
 }
 
@@ -3728,11 +3757,15 @@ rct_string_id network_get_action_name_string_id(uint32_t index)
 
 int32_t network_can_perform_action(uint32_t groupindex, uint32_t index)
 {
+    Guard::IndexInRange(groupindex, gNetwork.group_list);
+
     return gNetwork.group_list[groupindex]->CanPerformAction(index);
 }
 
 int32_t network_can_perform_command(uint32_t groupindex, int32_t index)
 {
+    Guard::IndexInRange(groupindex, gNetwork.group_list);
+
     return gNetwork.group_list[groupindex]->CanPerformCommand(index);
 }