diff --git a/src/gc.c b/src/gc.c
index 98ed32cd4a54a..65b52b7130dcc 100644
--- a/src/gc.c
+++ b/src/gc.c
@@ -1014,6 +1014,7 @@ STATIC_INLINE jl_value_t *jl_gc_big_alloc_inner(jl_ptls_t ptls, size_t sz)
     memset(v, 0xee, allocsz);
 #endif
     v->sz = allocsz;
+    v->header = 0;
     gc_big_object_link(ptls->gc_tls.heap.young_generation_of_bigvals, v);
     return jl_valueof(&v->header);
 }