diff --git a/FileBinaryMimeTypeGuesser.php b/FileBinaryMimeTypeGuesser.php
index d0c8d2b..1faa811 100644
--- a/FileBinaryMimeTypeGuesser.php
+++ b/FileBinaryMimeTypeGuesser.php
@@ -83,7 +83,7 @@ public function guessMimeType(string $path): ?string
 
         $type = trim(ob_get_clean());
 
-        if (!preg_match('#^([a-z0-9\-]+/[a-z0-9\-\.]+)#i', $type, $match)) {
+        if (!preg_match('#^([a-z0-9\-]+/[a-z0-9\-\+\.]+)#i', $type, $match)) {
             // it's not a type, but an error message
             return null;
         }