diff --git a/lib/sinatra/base.rb b/lib/sinatra/base.rb
index f90df8a48a..ca82ea4e00 100644
--- a/lib/sinatra/base.rb
+++ b/lib/sinatra/base.rb
@@ -341,7 +341,7 @@ def expires(amount, *values)
       values << {} unless values.last.kind_of?(Hash)
 
       if amount.is_a? Integer
-        time    = Time.now + amount
+        time    = Time.now + amount.to_i
         max_age = amount
       else
         time    = time_for amount