diff --git a/racket/src/racket/src/thread.c b/racket/src/racket/src/thread.c
index 2b56ba6f16..180527a689 100644
--- a/racket/src/racket/src/thread.c
+++ b/racket/src/racket/src/thread.c
@@ -193,7 +193,7 @@ THREAD_LOCAL_DECL(static Scheme_Custodian *last_custodian);
 THREAD_LOCAL_DECL(static Scheme_Hash_Table *limited_custodians = NULL);
 READ_ONLY static Scheme_Object *initial_inspector;
 
-THREAD_LOCAL_DECL(static Scheme_Custodian *initial_plumber);
+THREAD_LOCAL_DECL(static Scheme_Plumber *initial_plumber);
 
 THREAD_LOCAL_DECL(Scheme_Config *initial_config);