diff --git a/composer.json b/composer.json
index 5f9c946..42a3426 100644
--- a/composer.json
+++ b/composer.json
@@ -21,7 +21,7 @@
     },
     "require": {
         "php": ">=5.4.0",
-        "99designs/http-signatures": "~1.1",
+        "99designs/http-signatures": ">=1.1.0 <3.0.0",
         "guzzlehttp/guzzle": ">=4.2.0 <5.3.0"
     },
     "require-dev": {