diff --git a/lib/Component/VCard.php b/lib/Component/VCard.php
index 0b8696fd4..a31350084 100644
--- a/lib/Component/VCard.php
+++ b/lib/Component/VCard.php
@@ -531,6 +531,12 @@ public function getClassNameForPropertyName(string $propertyName): string
             return VObject\Property\Uri::class;
         }
 
+        // In vCard 4, KEY and SOUND are URIs by default too (RFC 6350, sections
+        // 6.7.5 and 6.8.1), not text.
+        if (in_array($propertyName, ['KEY', 'SOUND'], true) && self::VCARD40 === $this->getDocumentType()) {
+            return VObject\Property\Uri::class;
+        }
+
         return $className;
     }
 }
diff --git a/tests/VObject/Component/VCardKeySoundTest.php b/tests/VObject/Component/VCardKeySoundTest.php
new file mode 100644
index 000000000..ea8d6e32e
--- /dev/null
+++ b/tests/VObject/Component/VCardKeySoundTest.php
@@ -0,0 +1,44 @@
+<?php
+
+namespace Sabre\VObject\Component;
+
+use PHPUnit\Framework\TestCase;
+use Sabre\VObject\Document;
+use Sabre\VObject\Property;
+use Sabre\VObject\Reader;
+
+class VCardKeySoundTest extends TestCase
+{
+    public function testKeyAndSoundAreUrisInVCard40(): void
+    {
+        $vcard = Reader::read("BEGIN:VCARD\r\nVERSION:4.0\r\nKEY:https://example.com/key.asc\r\nSOUND:https://example.com/name.wav\r\nEND:VCARD\r\n");
+
+        self::assertInstanceOf(Property\Uri::class, $vcard->KEY);
+        self::assertInstanceOf(Property\Uri::class, $vcard->SOUND);
+        self::assertEquals(['key', new \stdClass(), 'uri', 'https://example.com/key.asc'], $vcard->KEY->jsonSerialize());
+    }
+
+    public function testATextKeyStaysText(): void
+    {
+        $vcard = Reader::read("BEGIN:VCARD\r\nVERSION:4.0\r\nKEY;VALUE=text:-----BEGIN PGP PUBLIC KEY BLOCK-----\r\nEND:VCARD\r\n");
+
+        self::assertInstanceOf(Property\Text::class, $vcard->KEY);
+    }
+
+    public function testVCard30IsUnchanged(): void
+    {
+        $vcard = Reader::read("BEGIN:VCARD\r\nVERSION:3.0\r\nKEY:https://example.com/key.asc\r\nEND:VCARD\r\n");
+
+        self::assertInstanceOf(Property\FlatText::class, $vcard->KEY);
+    }
+
+    public function testSoundDataUriConvertsToBinaryInVCard30(): void
+    {
+        $vcard = Reader::read("BEGIN:VCARD\r\nVERSION:4.0\r\nSOUND:data:audio/wav;base64,UklGRg==\r\nEND:VCARD\r\n");
+
+        $converted = $vcard->convert(Document::VCARD30);
+
+        self::assertInstanceOf(Property\Binary::class, $converted->SOUND);
+        self::assertEquals('RIFF', $converted->SOUND->getValue());
+    }
+}
diff --git a/tests/VObject/Parser/XmlTest.php b/tests/VObject/Parser/XmlTest.php
index 223b0f105..6ab8c4753 100644
--- a/tests/VObject/Parser/XmlTest.php
+++ b/tests/VObject/Parser/XmlTest.php
@@ -2455,7 +2455,7 @@ public function testRFC6350Section6Part7Part5(): void
 <vcards xmlns="urn:ietf:params:xml:ns:vcard-4.0">
  <vcard>
   <sound>
-   <text>CID:JOHNQPUBLIC.part8.19960229T080000.xyzMail@example.com</text>
+   <uri>CID:JOHNQPUBLIC.part8.19960229T080000.xyzMail@example.com</uri>
   </sound>
  </vcard>
 </vcards>
@@ -2571,7 +2571,7 @@ public function testRFC6350Section6Part8Part1(): void
      <text>application/pgp-keys</text>
     </mediatype>
    </parameters>
-   <text>ftp://example.com/keys/jdoe</text>
+   <uri>ftp://example.com/keys/jdoe</uri>
   </key>
  </vcard>
 </vcards>