diff --git a/src/json/ext/GeneratorState.java b/src/json/ext/GeneratorState.java
index 63263e8..7d6013b 100644
--- a/src/json/ext/GeneratorState.java
+++ b/src/json/ext/GeneratorState.java
@@ -131,7 +131,7 @@ static GeneratorState fromState(ThreadContext context, RuntimeInfo info,
         }
 
         // for other values, return the safe prototype
-        return info.getSafeStatePrototype(context);
+        return (GeneratorState)info.getSafeStatePrototype(context).dup();
     }
 
     /**