diff --git a/src/ActivityPhp/Server/Http/HttpSignature.php b/src/ActivityPhp/Server/Http/HttpSignature.php
index 1d87992..85d5cfd 100644
--- a/src/ActivityPhp/Server/Http/HttpSignature.php
+++ b/src/ActivityPhp/Server/Http/HttpSignature.php
@@ -28,7 +28,7 @@ class HttpSignature
             ([\w\-\.#\/@]+)
         )",
         (algorithm="(?P<algorithm>[\w\s-]+)",)?
-        (headers="\(request-target\) (?P<headers>[\w\s]+)",)?
+        (headers="\(request-target\) (?P<headers>[\w\s-]+)",)?
         signature="(?P<signature>[\w+\/]+={0,2})"
     /x';