diff --git a/lib/aws/s3/presigned_post.rb b/lib/aws/s3/presigned_post.rb
index 569639b21e9..d45c6027e1f 100644
--- a/lib/aws/s3/presigned_post.rb
+++ b/lib/aws/s3/presigned_post.rb
@@ -207,7 +207,7 @@ def initialize(bucket, opts = {})
         @content_length = range_value(opts[:content_length])
         @conditions = opts[:conditions] || {}
         @ignored_fields = [opts[:ignore]].flatten.compact
-        @expires = opts[:expires]
+        @expires = opts[:expires] || Time.now.utc + 60*60
 
         super
 
@@ -397,17 +397,16 @@ def with_condition(field, condition)
       # @api private
       private
       def format_expiration
-        time = expires || Time.now.utc + 60*60
         time =
-          case time
+          case expires
           when Time
-            time
+            expires
           when DateTime
-            Time.parse(time.to_s)
+            Time.parse(expires.to_s)
           when Integer
-            (Time.now + time)
+            (Time.now + expires)
           when String
-            Time.parse(time)
+            Time.parse(expires)
           end
         time.utc.iso8601
       end
diff --git a/spec/aws/s3/presigned_post_spec.rb b/spec/aws/s3/presigned_post_spec.rb
index 6278d23021d..c4be026af0c 100644
--- a/spec/aws/s3/presigned_post_spec.rb
+++ b/spec/aws/s3/presigned_post_spec.rb
@@ -352,6 +352,17 @@ def policy_conditions(post)
           policy["expiration"].should == "2011-05-25T01:51:04Z"
         end
 
+        it "should reuse the default expire set during initialize" do
+          now = Time.parse("2011-05-24T17:54:04-07:00Z")
+          Time.stub(:now).and_return(now)
+          policy["expiration"].should == "2011-05-25T01:54:04Z"
+
+          later = Time.parse("2011-05-24T17:54:05-07:00Z")
+          Time.stub(:now).and_return(later)
+          later_policy = JSON.load(Base64.decode64(post.policy))
+          later_policy["expiration"].should == "2011-05-25T01:54:04Z"
+        end
+
         context 'when :expires is provided' do
 
           it 'should support Time' do