diff --git a/plugins/Toolbox/src/Toolbox.py b/plugins/Toolbox/src/Toolbox.py
index 48219494bd..52b00f5069 100644
--- a/plugins/Toolbox/src/Toolbox.py
+++ b/plugins/Toolbox/src/Toolbox.py
@@ -818,7 +818,7 @@ class Toolbox(QObject, Extension):
         self._metadata["materials_showcase"] = []
         self._metadata["materials_available"] = []
 
-        processed_authors = []
+        processed_authors = [] # type: List[str]
 
         for item in self._metadata["packages"]:
             if item["package_type"] == "material":