diff --git a/src/cares_wrap.cc b/src/cares_wrap.cc
index 7be1e176654b64..6f8e8d89034123 100644
--- a/src/cares_wrap.cc
+++ b/src/cares_wrap.cc
@@ -627,6 +627,7 @@ Maybe<int> ParseTxtReply(Environment* env,
     // Each TXT record is a chunk consisting of one or more character-strings.
     LocalVector<Value> chunks(env->isolate());
     size_t str_count = ares_dns_rr_get_abin_cnt(rr, ARES_RR_TXT_DATA);
+    chunks.reserve(str_count);
     for (size_t j = 0; j < str_count; j++) {
       size_t str_len = 0;
       const unsigned char* str =
diff --git a/src/node_messaging.cc b/src/node_messaging.cc
index f00ab803fef089..cdccdd8ee6d5b7 100644
--- a/src/node_messaging.cc
+++ b/src/node_messaging.cc
@@ -486,6 +486,7 @@ Maybe<bool> Message::Serialize(Environment* env,
   delegate.serializer = &serializer;
 
   LocalVector<ArrayBuffer> array_buffers(env->isolate());
+  array_buffers.reserve(transfer_list_v.length());
   for (uint32_t i = 0; i < transfer_list_v.length(); ++i) {
     Local<Value> entry_val = transfer_list_v[i];
     if (!entry_val->IsObject()) {