diff --git a/app/assets/javascripts/helpers/markdown_editor.js b/app/assets/javascripts/helpers/markdown_editor.js
index 6286434375f4fafc0a9887539594d4c1ff31a9f9..5da96bbf022003953ca8c8830d2e5499a2b42dcd 100644
--- a/app/assets/javascripts/helpers/markdown_editor.js
+++ b/app/assets/javascripts/helpers/markdown_editor.js
@@ -9,7 +9,8 @@ Diaspora.MarkdownEditor.prototype = {
     this.options = {
       resize: "none",
       onHidePreview: $.noop,
-      onPostPreview: $.noop
+      onPostPreview: $.noop,
+      onChange: function(e) { autosize.update(e.$textarea); }
     };
 
     $.extend(this.options, opts);
diff --git a/spec/javascripts/helpers/markdown_editor_spec.js b/spec/javascripts/helpers/markdown_editor_spec.js
index 73c0047badd9c9b535489ccf437e5edab5732490..55bc68942d12a5a4263fcf9cb57e85af06e6999d 100644
--- a/spec/javascripts/helpers/markdown_editor_spec.js
+++ b/spec/javascripts/helpers/markdown_editor_spec.js
@@ -31,6 +31,7 @@ describe("Diaspora.MarkdownEditor", function() {
 
     it("call $.fn.markdown with correct default options", function() {
       spyOn($.fn, "markdown");
+      spyOn(autosize, "update");
       this.target.initialize(this.$el, {});
       expect($.fn.markdown).toHaveBeenCalled();
       var args = $.fn.markdown.calls.mostRecent().args[0];
@@ -40,6 +41,9 @@ describe("Diaspora.MarkdownEditor", function() {
       expect(args.onPostPreview).toBe($.noop);
       expect(args.fullscreen).toEqual({enable: false, icons: {}});
       expect(args.hiddenButtons).toEqual(["cmdPreview"]);
+
+      args.onChange({$textarea: "el"});
+      expect(autosize.update).toHaveBeenCalledWith("el");
     });
 
     it("overrides fullscreen, hiddenButtons, language and onShow options", function() {