diff --git a/lib/gettext/extractor.ex b/lib/gettext/extractor.ex
index 284b794..2fc0e9a 100644
--- a/lib/gettext/extractor.ex
+++ b/lib/gettext/extractor.ex
@@ -299,12 +299,18 @@ defmodule Gettext.Extractor do
   def merge_template(existing, new, gettext_config) do
     protected_pattern = gettext_config[:excluded_refs_from_purging]
 
+    # Index both sides by message key so that matching is linear rather than
+    # quadratic in the number of messages. The first message for a key wins,
+    # which is what Expo.Messages.find/2 returns.
+    new_by_key = Enum.reduce(new.messages, %{}, &Map.put_new(&2, Message.key(&1), &1))
+    existing_keys = MapSet.new(existing.messages, &Message.key/1)
+
     # We go over the existing message in order so as to keep the existing
     # order as much as possible.
     old_and_merged =
       Enum.flat_map(existing.messages, fn message ->
         cond do
-          same = Messages.find(new, message) -> [merge_message(message, same)]
+          same = Map.get(new_by_key, Message.key(message)) -> [merge_message(message, same)]
           protected?(message, protected_pattern) -> [message]
           autogenerated?(message) -> []
           true -> [message]
@@ -313,7 +319,7 @@ defmodule Gettext.Extractor do
 
     # We reject all messages that appear in `existing` so that we're left
     # with the messages that only appear in `new`.
-    unique_new = Enum.reject(new.messages, &Messages.find(existing, &1))
+    unique_new = Enum.reject(new.messages, &MapSet.member?(existing_keys, Message.key(&1)))
 
     messages = old_and_merged ++ unique_new