diff --git a/CHANGELOG.txt b/CHANGELOG.txt
index 8bc5045fc4..7007efec55 100644
--- a/CHANGELOG.txt
+++ b/CHANGELOG.txt
@@ -36,6 +36,7 @@ Changelog
  * Fix: Search indexing now uses a defined query ordering to prevent objects from being skipped (Christian Peters)
  * Fix: Ensure that number localisation is not applied to object IDs within admin templates (Tom Hendrikx)
  * Fix: Paginating with a search present was always returning the 1st page in Internet Explorer 10 & 11 (Ralph Jacobs)
+ * Fix: RoutablePageMixin and wagtailforms previews now set the `request.is_preview` flag (Wietze Helmantel)
 
 
 1.9 (16.02.2017)
diff --git a/CONTRIBUTORS.rst b/CONTRIBUTORS.rst
index c1e1e31a1a..7b48787fa3 100644
--- a/CONTRIBUTORS.rst
+++ b/CONTRIBUTORS.rst
@@ -220,6 +220,7 @@ Contributors
 * hdnpl
 * Tom Hendrikx
 * Ralph Jacobs
+* Wietze Helmantel
 
 Translators
 ===========
diff --git a/docs/releases/1.10.rst b/docs/releases/1.10.rst
index 90db7ceb32..d65b484885 100644
--- a/docs/releases/1.10.rst
+++ b/docs/releases/1.10.rst
@@ -48,6 +48,7 @@ Bug fixes
  * Search indexing now uses a defined query ordering to prevent objects from being skipped (Christian Peters)
  * Ensure that number localisation is not applied to object IDs within admin templates (Tom Hendrikx)
  * Paginating with a search present was always returning the 1st page in Internet Explorer 10 & 11 (Ralph Jacobs)
+ * RoutablePageMixin and wagtailforms previews now set the ``request.is_preview`` flag (Wietze Helmantel)
 
 
 Upgrade considerations
diff --git a/wagtail/contrib/wagtailroutablepage/models.py b/wagtail/contrib/wagtailroutablepage/models.py
index c00bfd29a4..351c28a65f 100644
--- a/wagtail/contrib/wagtailroutablepage/models.py
+++ b/wagtail/contrib/wagtailroutablepage/models.py
@@ -104,6 +104,8 @@ class RoutablePageMixin(object):
 
     def serve_preview(self, request, mode_name):
         view, args, kwargs = self.resolve_subpage('/')
+        request.is_preview = True
+
         return view(request, *args, **kwargs)
 
 
diff --git a/wagtail/wagtailforms/models.py b/wagtail/wagtailforms/models.py
index d3ac520646..68a1d5c541 100644
--- a/wagtail/wagtailforms/models.py
+++ b/wagtail/wagtailforms/models.py
@@ -266,6 +266,8 @@ class AbstractForm(Page):
 
     def serve_preview(self, request, mode):
         if mode == 'landing':
+            request.is_preview = True
+
             return render(
                 request,
                 self.get_landing_page_template(request),