diff --git a/lib/directive.js b/lib/directive.js
index c5ba920..63d39b0 100644
--- a/lib/directive.js
+++ b/lib/directive.js
@@ -115,9 +115,13 @@ Slingshot.Directive = function (service, directive) {
 
   _.defaults(directive, service.directiveDefault);
 
-  check(directive, _.defaults({
+  check(directive, _.extend({
     authorize: Function,
-    maxSize: Match.OneOf(Number, null),
+    maxSize: Match.Where(function (size) {
+      check(size, Match.OneOf(Number, null));
+
+      return !size || size > 0 && size <= (service.maxSize || Infinity);
+    }),
     allowedFileTypes: matchAllowedFileTypes,
     cdn: Match.Optional(String)
   }, service.directiveMatch));
@@ -223,9 +227,8 @@ _.extend(Slingshot.Directive.prototype, {
    */
 
   getInstructions: function (method, file, meta) {
-    var instructions = this.storageService().upload(method, _.extend({
-      contentDisposition: "inline; filename=" + quoteString(file.name, '"')
-    }, this._directive), file, meta);
+    var instructions = this.storageService().upload(method, this._directive,
+      file, meta);
 
     check(instructions, {
       upload: String,
@@ -302,7 +305,3 @@ function formatBytes(size) {
   return (Math.round(size * 100) / 100) + " " + unit;
 }
 
-
-function quoteString(string, quotes) {
-  return quotes + string.replace(quotes, '\\' + quotes) + quotes;
-}
diff --git a/services/aws-s3.js b/services/aws-s3.js
index ee23862..ada8810 100644
--- a/services/aws-s3.js
+++ b/services/aws-s3.js
@@ -76,7 +76,8 @@ Slingshot.S3Storage = {
           "acl": directive.acl,
 
           "Cache-Control": directive.cacheControl,
-          "Content-Disposition": directive.contentDisposition
+          "Content-Disposition": directive.contentDisposition ||
+            "inline; filename=" + quoteString(file.name, '"')
         },
 
         bucketUrl = _.isFunction(directive.bucketUrl) ?
@@ -120,3 +121,7 @@ Slingshot.S3Storage = {
       .digest("base64");
   }
 };
+
+function quoteString(string, quotes) {
+  return quotes + string.replace(quotes, '\\' + quotes) + quotes;
+}