diff --git a/src/dev-util/savegame.gd b/src/dev-util/savegame.gd
index 1b6058e..87f6560 100644
--- a/src/dev-util/savegame.gd
+++ b/src/dev-util/savegame.gd
@@ -11,10 +11,9 @@ class_name SaveGame extends Resource
 
 @export var is_save_file_valid: bool = false
 
-# FIXME: for some reason this does not prevent the property from being saved.
 func _validate_property(property: Dictionary):
 	if property.name == "thumbnail":
-		property.usage != PROPERTY_USAGE_STORAGE
+		property.usage = not PROPERTY_USAGE_STORAGE
 
 
 func _init(filepath = "") -> void: