diff --git a/runtime.c b/runtime.c
index 07e20fe9..494b9c35 100644
--- a/runtime.c
+++ b/runtime.c
@@ -2811,20 +2811,46 @@ object Cyc_bytevector_length(void *data, object bv)
 object Cyc_list2vector(void *data, object cont, object l)
 {
   object v = NULL;
-  object len;
+  object len_obj;
   object lst = l;
-  int i = 0;
+  int len, i = 0;
+  size_t element_vec_size;
 
+  make_c_opaque(opq, NULL);
   Cyc_check_pair_or_null(data, l);
-  len = Cyc_length(data, l);
-  v = alloca(sizeof(vector_type));
-  ((vector) v)->hdr.mark = gc_color_red;
-  ((vector) v)->hdr.grayed = 0;
-  ((vector) v)->tag = vector_tag;
-  ((vector) v)->num_elements = obj_obj2int(len);
-  ((vector) v)->elements =
-      (((vector) v)->num_elements > 0) ?
-      (object *) alloca(sizeof(object) * ((vector) v)->num_elements) : NULL;
+  len_obj = Cyc_length(data, l);
+  len = obj_obj2int(len_obj);
+  element_vec_size = sizeof(object) * len;
+  if (element_vec_size >= MAX_STACK_OBJ) {
+    int heap_grown;
+    v = gc_alloc(((gc_thread_data *)data)->heap, 
+                 sizeof(vector_type) + element_vec_size,
+                 boolean_f, // OK to populate manually over here
+                 (gc_thread_data *)data, 
+                 &heap_grown);
+    ((vector) v)->hdr.mark = ((gc_thread_data *)data)->gc_alloc_color;
+    ((vector) v)->hdr.grayed = 0;
+    ((vector) v)->tag = vector_tag;
+    ((vector) v)->num_elements = len;
+    ((vector) v)->elements = (object *)(((char *)v) + sizeof(vector_type));
+    // TODO: do we need to worry about stack object in the list????
+    //// Use write barrier to ensure fill is moved to heap if it is on the stack
+    //// Otherwise if next minor GC misses fill it could be catastrophic
+    //car(&tmp_pair) = fill;
+    //add_mutation(data, &tmp_pair, -1, fill);
+    // Add a special object to indicate full vector must be scanned by GC
+    opaque_ptr(&opq) = v;
+    add_mutation(data, &opq, -1, v);
+  } else {
+    v = alloca(sizeof(vector_type));
+    ((vector) v)->hdr.mark = gc_color_red;
+    ((vector) v)->hdr.grayed = 0;
+    ((vector) v)->tag = vector_tag;
+    ((vector) v)->num_elements = len;
+    ((vector) v)->elements =
+        (((vector) v)->num_elements > 0) ?
+        (object *) alloca(element_vec_size) : NULL;
+  }
   while ((lst != NULL)) {
     ((vector) v)->elements[i++] = car(lst);
     lst = cdr(lst);