1 files changed, 0 insertions, 1 deletions
diff --git a/gc.c b/gc.c
index aab0963c29..f8e2513ff4 100644
--- a/gc.c
+++ b/gc.c
@@ -491,7 +491,6 @@ rb_objspace_free(rb_objspace_t *objspace)
 
 #define HEAP_OBJ_LIMIT (HEAP_SIZE / sizeof(struct RVALUE))
 
-extern VALUE rb_cMutex;
 extern st_table *rb_class_tbl;
 
 int ruby_disable_gc_stress = 0;