diff --git a/src/runtime/object.cpp b/src/runtime/object.cpp
index 654e1b59f29d..f10e6c57984c 100644
--- a/src/runtime/object.cpp
+++ b/src/runtime/object.cpp
@@ -2395,7 +2395,7 @@ extern "C" LEAN_EXPORT object * lean_array_push(obj_arg a, obj_arg v) {
         else
             r = lean_copy_expand_array(a, true);
     } else {
-        r = lean_copy_expand_array(a, lean_array_capacity(a) < 2*lean_array_size(a) + 1);
+        r = lean_copy_expand_array(a, lean_array_capacity(a) < lean_array_size(a) + 1);
     }
     lean_assert(lean_array_capacity(r) > lean_array_size(r));
     size_t & sz  = lean_to_array(r)->m_size;