diff --git a/components/net/resource_task.rs b/components/net/resource_task.rs
index 591e146af03..14d5e8fbba1 100644
--- a/components/net/resource_task.rs
+++ b/components/net/resource_task.rs
@@ -104,17 +104,17 @@ pub fn start_sending_sniffed_opt(start_chan: LoadConsumer, mut metadata: Metadat
 
         if let Some(ref headers) = metadata.headers {
             if let Some(ref raw_content_type) = headers.get_raw("content-type") {
-                let ref last_raw_content_type = raw_content_type[raw_content_type.len() - 1];
-                check_for_apache_bug = last_raw_content_type == b"text/plain"
-                                    || last_raw_content_type == b"text/plain; charset=ISO-8859-1"
-                                    || last_raw_content_type == b"text/plain; charset=iso-8859-1"
-                                    || last_raw_content_type == b"text/plain; charset=UTF-8";
-            }
-            if let Some(ref raw_content_type_options) = headers.get_raw("content-type-options") {
-                for options in raw_content_type_options.iter() {
-                    nosniff = nosniff || options == b"nosniff";
+                if raw_content_type.len() > 0 {
+                    let ref last_raw_content_type = raw_content_type[raw_content_type.len() - 1];
+                    check_for_apache_bug = last_raw_content_type == b"text/plain"
+                                        || last_raw_content_type == b"text/plain; charset=ISO-8859-1"
+                                        || last_raw_content_type == b"text/plain; charset=iso-8859-1"
+                                        || last_raw_content_type == b"text/plain; charset=UTF-8";
                 }
             }
+            if let Some(ref raw_content_type_options) = headers.get_raw("X-content-type-options") {
+                nosniff = raw_content_type_options.iter().any(|ref opt| *opt == b"nosniff");
+            }
         }
 
         let supplied_type = metadata.content_type.map(|ContentType(Mime(toplevel, sublevel, _))| {