diff --git a/lib/escher/auth.rb b/lib/escher/auth.rb
index 3ab0fad..45437e5 100644
--- a/lib/escher/auth.rb
+++ b/lib/escher/auth.rb
@@ -38,6 +38,8 @@ def is_valid?(*args)
       begin
         authenticate(*args)
         return true
+      rescue EscherError
+        return false
       rescue
         return false
       end