diff --git a/racket/src/racket/src/salloc.c b/racket/src/racket/src/salloc.c
index ff0f86f1fc..7f1b1d7633 100644
--- a/racket/src/racket/src/salloc.c
+++ b/racket/src/racket/src/salloc.c
@@ -54,6 +54,8 @@
 # include <windows.h>
 #endif
 
+THREAD_LOCAL_DECL(uintptr_t scheme_os_thread_id);
+
 THREAD_LOCAL_DECL(static void **dgc_array);
 THREAD_LOCAL_DECL(static int *dgc_count);
 THREAD_LOCAL_DECL(static int dgc_size);