--- a/devtools/client/styleeditor/test/browser.ini
+++ b/devtools/client/styleeditor/test/browser.ini
@@ -33,16 +33,17 @@ support-files =
   sourcemap-css/contained.css
   sourcemap-css/sourcemaps.css
   sourcemap-css/sourcemaps.css.map
   sourcemap-css/media-rules.css
   sourcemap-css/media-rules.css.map
   sourcemap-css/test-bootstrap-scss.css
   sourcemap-css/test-stylus.css
   sourcemap-sass/sourcemaps.scss
+  sourcemap-sass/sourcemaps.scss^headers^
   sourcemap-sass/media-rules.scss
   sourcemap-styl/test-stylus.styl
   sourcemaps.html
   sourcemaps-inline.html
   sourcemaps-large.html
   sourcemaps-watching.html
   test_private.css
   test_private.html

new file mode 100644
--- /dev/null
+++ b/devtools/client/styleeditor/test/sourcemap-sass/sourcemaps.scss^headers^
@@ -0,0 +1,2 @@
+X-Content-Type-Options: nosniff
+Content-Type: text/plain

--- a/devtools/server/actors/stylesheets.js
+++ b/devtools/server/actors/stylesheets.js
@@ -83,17 +83,22 @@ var OriginalSourceActor = protocol.Actor
       return promise.resolve(this.text);
     }
     let content = this.sourceMap.sourceContentFor(this.url);
     if (content) {
       this.text = content;
       return promise.resolve(content);
     }
     let options = {
-      policy: Ci.nsIContentPolicy.TYPE_INTERNAL_STYLESHEET,
+      // Make sure to use TYPE_OTHER - we are not fetching necessarily
+      // even fetching a style sheet, and anyway we're not planning to
+      // use it as a style sheet per se but rather just for its text;
+      // and this avoids problems with X-Content-Type-Options:
+      // nosniff.  See bug 1330383.
+      policy: Ci.nsIContentPolicy.TYPE_OTHER,
       window: this.window
     };
     return fetch(this.url, options).then(({content: text}) => {
       this.text = text;
       return text;
     });
   },