diff --git a/src/sim65/chiplib.h b/src/sim65/chiplib.h
index 29a5ebf44..f4a019fc3 100644
--- a/src/sim65/chiplib.h
+++ b/src/sim65/chiplib.h
@@ -64,7 +64,7 @@ struct ChipLibrary {
 };
 
 /* A collection containing all libraries */
-Collection ChipLibraries;
+extern Collection ChipLibraries;