diff --git a/MessageCatalogue.php b/MessageCatalogue.php
index 09153d12..4b8fc58d 100644
--- a/MessageCatalogue.php
+++ b/MessageCatalogue.php
@@ -156,19 +156,14 @@ public function replace(array $messages, string $domain = 'messages')
      */
     public function add(array $messages, string $domain = 'messages')
     {
-        if (!isset($this->messages[$domain])) {
-            $this->messages[$domain] = [];
-        }
-        $intlDomain = $domain;
-        if (!str_ends_with($domain, self::INTL_DOMAIN_SUFFIX)) {
-            $intlDomain .= self::INTL_DOMAIN_SUFFIX;
-        }
+        $altDomain = str_ends_with($domain, self::INTL_DOMAIN_SUFFIX) ? substr($domain, 0, -\strlen(self::INTL_DOMAIN_SUFFIX)) : $domain.self::INTL_DOMAIN_SUFFIX;
         foreach ($messages as $id => $message) {
-            if (isset($this->messages[$intlDomain]) && \array_key_exists($id, $this->messages[$intlDomain])) {
-                $this->messages[$intlDomain][$id] = $message;
-            } else {
-                $this->messages[$domain][$id] = $message;
-            }
+            unset($this->messages[$altDomain][$id]);
+            $this->messages[$domain][$id] = $message;
+        }
+
+        if ([] === ($this->messages[$altDomain] ?? null)) {
+            unset($this->messages[$altDomain]);
         }
     }
 
diff --git a/Tests/Catalogue/MergeOperationTest.php b/Tests/Catalogue/MergeOperationTest.php
index 3f21abac..1c9bcbc2 100644
--- a/Tests/Catalogue/MergeOperationTest.php
+++ b/Tests/Catalogue/MergeOperationTest.php
@@ -57,7 +57,7 @@ public function testGetResultFromIntlDomain()
     {
         $this->assertEquals(
             new MessageCatalogue('en', [
-                'messages' => ['a' => 'old_a', 'b' => 'old_b'],
+                'messages' => ['b' => 'old_b'],
                 'messages+intl-icu' => ['d' => 'old_d', 'c' => 'new_c', 'a' => 'new_a'],
             ]),
             $this->createOperation(
diff --git a/Tests/Catalogue/TargetOperationTest.php b/Tests/Catalogue/TargetOperationTest.php
index 2b63cd41..6f4de858 100644
--- a/Tests/Catalogue/TargetOperationTest.php
+++ b/Tests/Catalogue/TargetOperationTest.php
@@ -71,7 +71,6 @@ public function testGetResultWithMixedDomains()
     {
         $this->assertEquals(
             new MessageCatalogue('en', [
-                'messages' => ['a' => 'old_a'],
                 'messages+intl-icu' => ['a' => 'new_a'],
             ]),
             $this->createOperation(
@@ -103,7 +102,6 @@ public function testGetResultWithMixedDomains()
 
         $this->assertEquals(
             new MessageCatalogue('en', [
-                'messages' => ['a' => 'old_a'],
                 'messages+intl-icu' => ['b' => 'new_b', 'a' => 'new_a'],
             ]),
             $this->createOperation(
diff --git a/Tests/TranslatorTest.php b/Tests/TranslatorTest.php
index 57f5456d..b5c332df 100644
--- a/Tests/TranslatorTest.php
+++ b/Tests/TranslatorTest.php
@@ -15,6 +15,10 @@
 use Symfony\Component\Translation\Exception\InvalidArgumentException;
 use Symfony\Component\Translation\Exception\NotFoundResourceException;
 use Symfony\Component\Translation\Exception\RuntimeException;
+use Symfony\Component\Translation\Formatter\IntlFormatter;
+use Symfony\Component\Translation\Formatter\IntlFormatterInterface;
+use Symfony\Component\Translation\Formatter\MessageFormatter;
+use Symfony\Component\Translation\Formatter\MessageFormatterInterface;
 use Symfony\Component\Translation\Loader\ArrayLoader;
 use Symfony\Component\Translation\MessageCatalogue;
 use Symfony\Component\Translation\TranslatableMessage;
@@ -563,6 +567,26 @@ public function testIntlFormattedDomain()
         $this->assertSame('Hi Bob', $translator->trans('some_message', ['%name%' => 'Bob']));
     }
 
+    public function testIntlDomainOverlapseWithIntlResourceBefore()
+    {
+        $intlFormatterMock = $this->createMock(IntlFormatterInterface::class);
+        $intlFormatterMock->expects($this->once())->method('formatIntl')->with('hello intl', 'en', [])->willReturn('hello intl');
+
+        $messageFormatter = new MessageFormatter(null, $intlFormatterMock);
+
+        $translator = new Translator('en', $messageFormatter);
+        $translator->addLoader('array', new ArrayLoader());
+
+        $translator->addResource('array', ['some_message' => 'hello intl'], 'en', 'messages+intl-icu');
+        $translator->addResource('array', ['some_message' => 'hello'], 'en', 'messages');
+
+        $this->assertSame('hello', $translator->trans('some_message', [], 'messages'));
+
+        $translator->addResource('array', ['some_message' => 'hello intl'], 'en', 'messages+intl-icu');
+
+        $this->assertSame('hello intl', $translator->trans('some_message', [], 'messages'));
+    }
+
     public function testMissingLoaderForResourceError()
     {
         $this->expectException(RuntimeException::class);