diff --git a/src/addresses.h b/src/addresses.h
index e55b0cee86..55cd3f585d 100644
--- a/src/addresses.h
+++ b/src/addresses.h
@@ -126,6 +126,10 @@
 
 #define RCT2_ADDRESS_RUN_INTRO_TICK_PART			0x009AC319
 
+// 0 = none, 255 = load file, 254 = anything else
+#define RCT2_ADDRESS_ERROR_TYPE						0x009AC31B
+#define RCT2_ADDRESS_ERROR_STRING_ID				0x009AC31C
+
 #define RCT2_ADDRESS_WINDOW_MAP_FLASHING_FLAGS		0x009AC861
 
 #define RCT2_ADDRESS_RIDE_ENTRIES					0x009ACFA4
@@ -268,6 +272,9 @@
 
 #define RCT2_ADDRESS_SCENARIO_TEXT_TEMP_OBJECT		0x00F42BC8
 
+// 1 if custom objects installed, 0 otherwise
+#define RCT2_ADDRESS_CUSTOM_OBJECTS_INSTALLED		0x00F42BDA
+
 #define RCT2_ADDRESS_VOLUME_ADJUST_ZOOM				0x00F438AC
 
 #define RCT2_ADDRESS_STAFF_HIGHLIGHTED_INDEX		0x00F43908
diff --git a/src/editor.c b/src/editor.c
index 09e1eb8c76..600eddf059 100644
--- a/src/editor.c
+++ b/src/editor.c
@@ -588,8 +588,8 @@ static int editor_load_landscape_from_sv4(const char *path)
 	// Open file
 	fp = fopen(path, "rb");
 	if (fp == NULL) {
-		RCT2_GLOBAL(0x009AC31B, uint8) = 255;
-		RCT2_GLOBAL(0x009AC31C, uint16) = 3011;
+		RCT2_GLOBAL(RCT2_ADDRESS_ERROR_TYPE, uint8) = 255;
+		RCT2_GLOBAL(RCT2_ADDRESS_ERROR_STRING_ID, uint16) = 3011;
 		return 0;
 	}
 
@@ -615,8 +615,8 @@ static int editor_load_landscape_from_sc4(const char *path)
 	// Open file
 	fp = fopen(path, "rb");
 	if (fp == NULL) {
-		RCT2_GLOBAL(0x009AC31B, uint8) = 255;
-		RCT2_GLOBAL(0x009AC31C, uint16) = 3011;
+		RCT2_GLOBAL(RCT2_ADDRESS_ERROR_TYPE, uint8) = 255;
+		RCT2_GLOBAL(RCT2_ADDRESS_ERROR_STRING_ID, uint16) = 3011;
 		return 0;
 	}
 
@@ -759,8 +759,8 @@ static int editor_read_s6(const char *path)
 	if (file != NULL) {
 		if (!sawyercoding_validate_checksum(file)) {
 			fclose(file);
-			RCT2_GLOBAL(0x009AC31B, uint8) = 255;
-			RCT2_GLOBAL(0x009AC31C, uint16) = STR_FILE_CONTAINS_INVALID_DATA;
+			RCT2_GLOBAL(RCT2_ADDRESS_ERROR_TYPE, uint8) = 255;
+			RCT2_GLOBAL(RCT2_ADDRESS_ERROR_STRING_ID, uint16) = STR_FILE_CONTAINS_INVALID_DATA;
 
 			log_error("failed to load scenario, invalid checksum");
 			return 0;
@@ -963,8 +963,8 @@ static int editor_read_s6(const char *path)
 	}
 
 	log_error("failed to find scenario file.");
-	RCT2_GLOBAL(0x009AC31B, uint8) = 255;
-	RCT2_GLOBAL(0x009AC31C, uint16) = STR_FILE_CONTAINS_INVALID_DATA;
+	RCT2_GLOBAL(RCT2_ADDRESS_ERROR_TYPE, uint8) = 255;
+	RCT2_GLOBAL(RCT2_ADDRESS_ERROR_STRING_ID, uint16) = STR_FILE_CONTAINS_INVALID_DATA;
 	return 0;
 }
 
diff --git a/src/game.c b/src/game.c
index 707af12c5a..dc702c2d7e 100644
--- a/src/game.c
+++ b/src/game.c
@@ -298,8 +298,6 @@ void game_update()
 
 void game_logic_update()
 {
-	short stringId, _dx;
-
 	RCT2_GLOBAL(RCT2_ADDRESS_CURRENT_TICKS, sint32)++;
 	RCT2_GLOBAL(RCT2_ADDRESS_SCENARIO_TICKS, sint32)++;
 	RCT2_GLOBAL(0x009DEA66, sint16)++;
@@ -329,16 +327,16 @@ void game_logic_update()
 	// Update windows
 	window_dispatch_update_all();
 
-	if (RCT2_GLOBAL(0x009AC31B, uint8) != 0) {
-		stringId = STR_UNABLE_TO_LOAD_FILE;
-		_dx = RCT2_GLOBAL(0x009AC31C, uint16);
-		if (RCT2_GLOBAL(0x009AC31B, uint8) != 254) {
-			stringId = RCT2_GLOBAL(0x009AC31C, uint16);
-			_dx = 0xFFFF;
+	if (RCT2_GLOBAL(RCT2_ADDRESS_ERROR_TYPE, uint8) != 0) {
+		rct_string_id title_text = STR_UNABLE_TO_LOAD_FILE;
+		rct_string_id body_text = RCT2_GLOBAL(RCT2_ADDRESS_ERROR_STRING_ID, uint16);
+		if (RCT2_GLOBAL(RCT2_ADDRESS_ERROR_TYPE, uint8) == 254) {
+			title_text = RCT2_GLOBAL(RCT2_ADDRESS_ERROR_STRING_ID, uint16);
+			body_text = 0xFFFF;
 		}
-		RCT2_GLOBAL(0x009AC31B, uint8) = 0;
+		RCT2_GLOBAL(RCT2_ADDRESS_ERROR_TYPE, uint8) = 0;
 
-		window_error_open(stringId, _dx);
+		window_error_open(title_text, body_text);
 	}
 }
 
@@ -601,7 +599,7 @@ int game_load_save(const char *path)
 	if (file == NULL) {
 		log_error("unable to open %s", path);
 
-		RCT2_GLOBAL(0x009AC31B, uint8) = 255;
+		RCT2_GLOBAL(RCT2_ADDRESS_ERROR_TYPE, uint8) = 255;
 		RCT2_GLOBAL(RCT2_ADDRESS_GAME_COMMAND_ERROR_STRING_ID, uint16) = STR_FILE_CONTAINS_INVALID_DATA;
 		return 0;
 	}
@@ -611,7 +609,7 @@ int game_load_save(const char *path)
 
 		log_error("invalid checksum, %s", path);
 
-		RCT2_GLOBAL(0x009AC31B, uint8) = 255;
+		RCT2_GLOBAL(RCT2_ADDRESS_ERROR_TYPE, uint8) = 255;
 		RCT2_GLOBAL(RCT2_ADDRESS_GAME_COMMAND_ERROR_STRING_ID, uint16) = STR_FILE_CONTAINS_INVALID_DATA;
 		return 0;
 	}
diff --git a/src/object_list.c b/src/object_list.c
index ed9e7f809a..6de10f3a3a 100644
--- a/src/object_list.c
+++ b/src/object_list.c
@@ -153,10 +153,12 @@ static void object_list_examine()
 	int i;
 	rct_object_entry *object;
 
+	RCT2_GLOBAL(RCT2_ADDRESS_CUSTOM_OBJECTS_INSTALLED, uint8) = 0;
+
 	object = RCT2_GLOBAL(RCT2_ADDRESS_INSTALLED_OBJECT_LIST, rct_object_entry*);
 	for (i = 0; i < RCT2_GLOBAL(RCT2_ADDRESS_OBJECT_LIST_NO_ITEMS, sint32); i++) {
-		if (object->flags & 0xF0)
-			RCT2_GLOBAL(0x00F42BDA, uint8) |= 1;
+		if (!(object->flags & 0xF0))
+			RCT2_GLOBAL(RCT2_ADDRESS_CUSTOM_OBJECTS_INSTALLED, uint8) |= 1;
 
 		object = object_get_next(object);
 	}
@@ -297,7 +299,7 @@ void object_list_load()
 
 	object_list_cache_save(fileCount, totalFileSize, fileDateModifiedChecksum, current_item_offset);
 
-	// 
+	// Reload track list
 	ride_list_item ride_list;
 	ride_list.entry_index = 0xFC;
 	ride_list.type = 0xFC;
@@ -402,15 +404,15 @@ void set_load_objects_fail_reason(){
 		format_string(string_buffer, 3323, 0); //Missing object data, ID:
 
 		RCT2_CALLPROC_X(0x6AB344, 0, 0, 0, 0, 0, (int)string_buffer, 0x13CE952);
-		RCT2_GLOBAL(0x9AC31B, uint8) = 0xFF;
-		RCT2_GLOBAL(0x9AC31C, uint16) = 3165;
+		RCT2_GLOBAL(RCT2_ADDRESS_ERROR_TYPE, uint8) = 0xFF;
+		RCT2_GLOBAL(RCT2_ADDRESS_ERROR_STRING_ID, uint16) = 3165;
 		return;
 	}
 
 	char* exapansion_name = &RCT2_ADDRESS(RCT2_ADDRESS_EXPANSION_NAMES, char)[128 * expansion];
 	if (*exapansion_name == '\0'){
-		RCT2_GLOBAL(0x9AC31B, uint8) = 0xFF;
-		RCT2_GLOBAL(0x9AC31C, uint16) = 3325;
+		RCT2_GLOBAL(RCT2_ADDRESS_ERROR_TYPE, uint8) = 0xFF;
+		RCT2_GLOBAL(RCT2_ADDRESS_ERROR_STRING_ID, uint16) = 3325;
 		return;
 	}
 
@@ -418,8 +420,8 @@ void set_load_objects_fail_reason(){
 
 	format_string(string_buffer, 3324, 0); // Requires expansion pack
 	strcat(string_buffer, exapansion_name);
-	RCT2_GLOBAL(0x9AC31B, uint8) = 0xFF;
-	RCT2_GLOBAL(0x9AC31C, uint16) = 3165;
+	RCT2_GLOBAL(RCT2_ADDRESS_ERROR_TYPE, uint8) = 0xFF;
+	RCT2_GLOBAL(RCT2_ADDRESS_ERROR_STRING_ID, uint16) = 3165;
 }
 
 /**
@@ -595,7 +597,9 @@ static uint32 install_object_entry(rct_object_entry* entry, rct_object_entry* in
 
 	// Chunk size is set to unknown
 	*((sint32*)installed_entry_pointer) = -1;
+	// No unknown objects set to 0
 	*(installed_entry_pointer + 4) = 0;
+	// No theme objects set to 0
 	*((sint32*)(installed_entry_pointer + 5)) = 0;
 	*((uint16*)(installed_entry_pointer + 9)) = 0;
 	*((uint32*)(installed_entry_pointer + 11)) = 0;
diff --git a/src/scenario.c b/src/scenario.c
index 65158dbffe..242dfc6b23 100644
--- a/src/scenario.c
+++ b/src/scenario.c
@@ -82,8 +82,8 @@ int scenario_load_basic(const char *path, rct_s6_header *header, rct_s6_info *in
 	}
 
 	log_error("invalid scenario, %s", path);
-	// RCT2_GLOBAL(0x009AC31B, sint8) = -1;
-	// RCT2_GLOBAL(0x009AC31C, sint16) = 3011;
+	// RCT2_GLOBAL(RCT2_ADDRESS_ERROR_TYPE, sint8) = -1;
+	// RCT2_GLOBAL(RCT2_ADDRESS_ERROR_STRING_ID, sint16) = 3011;
 	return 0;
 }
 
@@ -105,8 +105,8 @@ int scenario_load(const char *path)
 	if (file != NULL) {
 		if (!sawyercoding_validate_checksum(file)) {
 			fclose(file);
-			RCT2_GLOBAL(0x009AC31B, uint8) = 255;
-			RCT2_GLOBAL(0x009AC31C, uint16) = STR_FILE_CONTAINS_INVALID_DATA;
+			RCT2_GLOBAL(RCT2_ADDRESS_ERROR_TYPE, uint8) = 255;
+			RCT2_GLOBAL(RCT2_ADDRESS_ERROR_STRING_ID, uint16) = STR_FILE_CONTAINS_INVALID_DATA;
 
 			log_error("failed to load scenario, invalid checksum");
 			return 0;
@@ -182,8 +182,8 @@ int scenario_load(const char *path)
 	}
 
 	log_error("failed to find scenario file.");
-	RCT2_GLOBAL(0x009AC31B, uint8) = 255;
-	RCT2_GLOBAL(0x009AC31C, uint16) = STR_FILE_CONTAINS_INVALID_DATA;
+	RCT2_GLOBAL(RCT2_ADDRESS_ERROR_TYPE, uint8) = 255;
+	RCT2_GLOBAL(RCT2_ADDRESS_ERROR_STRING_ID, uint16) = STR_FILE_CONTAINS_INVALID_DATA;
 	return 0;
 }
 
diff --git a/src/windows/options.c b/src/windows/options.c
index 0d959a466b..a7fc5f3934 100644
--- a/src/windows/options.c
+++ b/src/windows/options.c
@@ -803,7 +803,7 @@ static void window_options_invalidate()
 			w->disabled_widgets |= (1ULL << WIDX_REAL_NAME_CHECKBOX);
 
 		// save plugin data checkbox: visible or not
-		if (RCT2_GLOBAL(0x00F42BDA, uint8) == 1)
+		if (RCT2_GLOBAL(RCT2_ADDRESS_CUSTOM_OBJECTS_INSTALLED, uint8) == 1)
 			window_options_widgets[WIDX_SAVE_PLUGIN_DATA_CHECKBOX].type = WWT_EMPTY;
 		else
 			window_options_widgets[WIDX_SAVE_PLUGIN_DATA_CHECKBOX].type = WWT_CHECKBOX;