diff --git a/.phan/config.php b/.phan/config.php
index a1e36bb8eda..13f913885e3 100644
--- a/.phan/config.php
+++ b/.phan/config.php
@@ -26,6 +26,7 @@ $cfg['file_list'] = array_merge(
 	class_exists( PEAR::class ) ? [] : [ '.phan/stubs/mail.php' ],
 	defined( 'PASSWORD_ARGON2ID' ) ? [] : [ '.phan/stubs/password.php' ],
 	class_exists( ExcimerProfiler::class ) ? [] : [ '.phan/stubs/excimer.php' ],
+	class_exists( ValueError::class ) ? [] : [ '.phan/stubs/ValueError.php' ],
 	[
 		// This makes constants and globals known to Phan before processing all other files.
 		// You can check the parser order with --dump-parsed-file-list
diff --git a/.phan/stubs/ValueError.php b/.phan/stubs/ValueError.php
new file mode 100644
index 00000000000..64a9450dbbc
--- /dev/null
+++ b/.phan/stubs/ValueError.php
@@ -0,0 +1,6 @@
+<?php
+
+// Stub for PHP 8's ValueError exception
+
+class ValueError extends Error {
+}
diff --git a/includes/password/Pbkdf2Password.php b/includes/password/Pbkdf2Password.php
index 816df7ced19..a2336031deb 100644
--- a/includes/password/Pbkdf2Password.php
+++ b/includes/password/Pbkdf2Password.php
@@ -48,16 +48,23 @@ class Pbkdf2Password extends ParameterizedPassword {
 			$this->args[] = base64_encode( random_bytes( 16 ) );
 		}
 
-		$hash = hash_pbkdf2(
-			$this->params['algo'],
-			$password,
-			base64_decode( $this->args[0] ),
-			(int)$this->params['rounds'],
-			(int)$this->params['length'],
-			true
-		);
-		if ( !is_string( $hash ) ) {
-			throw new PasswordError( 'Error when hashing password.' );
+		try {
+			$hash = hash_pbkdf2(
+				$this->params['algo'],
+				$password,
+				base64_decode( $this->args[0] ),
+				(int)$this->params['rounds'],
+				(int)$this->params['length'],
+				true
+			);
+
+			// PHP < 8 raises a warning in case of an error, such as unknown algorithm...
+			if ( !is_string( $hash ) ) {
+				throw new PasswordError( 'Error when hashing password.' );
+			}
+		} catch ( ValueError $e ) {
+			// ...while PHP 8 throws ValueError
+			throw new PasswordError( 'Error when hashing password.', 0, $e );
 		}
 
 		$this->hash = base64_encode( $hash );