diff --git a/src/Composer/Package/Archiver/ArchiverInterface.php b/src/Composer/Package/Archiver/ArchiverInterface.php
index f19b2c285..8b3ef316b 100644
--- a/src/Composer/Package/Archiver/ArchiverInterface.php
+++ b/src/Composer/Package/Archiver/ArchiverInterface.php
@@ -36,9 +36,9 @@ interface ArchiverInterface
      * Format supported by the archiver.
      *
      * @param string $format     The archive format
-     * @param string $sourceType The source type (git, svn, hg, etc.)
+     * @param ?string $sourceType The source type (git, svn, hg, etc.)
      *
      * @return bool true if the format is supported by the archiver
      */
-    public function supports(string $format, string $sourceType): bool;
+    public function supports(string $format, ?string $sourceType): bool;
 }
diff --git a/src/Composer/Package/Archiver/PharArchiver.php b/src/Composer/Package/Archiver/PharArchiver.php
index 225a4a91a..a0131bb54 100644
--- a/src/Composer/Package/Archiver/PharArchiver.php
+++ b/src/Composer/Package/Archiver/PharArchiver.php
@@ -97,7 +97,7 @@ class PharArchiver implements ArchiverInterface
     /**
      * @inheritDoc
      */
-    public function supports(string $format, string $sourceType): bool
+    public function supports(string $format, ?string $sourceType): bool
     {
         return isset(static::$formats[$format]);
     }
diff --git a/src/Composer/Package/Archiver/ZipArchiver.php b/src/Composer/Package/Archiver/ZipArchiver.php
index 8c655f6a0..fce4f14bc 100644
--- a/src/Composer/Package/Archiver/ZipArchiver.php
+++ b/src/Composer/Package/Archiver/ZipArchiver.php
@@ -78,7 +78,7 @@ class ZipArchiver implements ArchiverInterface
     /**
      * @inheritDoc
      */
-    public function supports(string $format, string $sourceType): bool
+    public function supports(string $format, ?string $sourceType): bool
     {
         return isset(static::$formats[$format]) && $this->compressionAvailable();
     }