diff --git a/docs/source/api/python/mantid/api/MultipleFileProperty.rst b/docs/source/api/python/mantid/api/MultipleFileProperty.rst
index 2dfea95c93092c09e50b88b346feb93cdd10436d..77fa697b88bf3d5ceb0e9141006bb8edb74ddc78 100644
--- a/docs/source/api/python/mantid/api/MultipleFileProperty.rst
+++ b/docs/source/api/python/mantid/api/MultipleFileProperty.rst
@@ -130,3 +130,5 @@ Detailed API Documentation
     :members:
     :undoc-members:
     :inherited-members:
+
+.. categories:: Concepts
diff --git a/docs/sphinxext/mantiddoc/directives/categories.py b/docs/sphinxext/mantiddoc/directives/categories.py
index cf24766ab61334cdb8a25c4111389ad1857cc5d9..0fd36f5f316b27dba717cd8076d627457963e597 100644
--- a/docs/sphinxext/mantiddoc/directives/categories.py
+++ b/docs/sphinxext/mantiddoc/directives/categories.py
@@ -348,14 +348,14 @@ def create_category_pages(app):
         # Now any additional index pages if required
         if category.name in INDEX_CATEGORIES:
             # index in categories directory
-            category_html_dir = os.path.dirname(category.html_path)
-            category_html_path_noext = category_html_dir + "/index"
+            category_html_dir = os.path.join(category.name.lower(), 'categories')
+            category_html_path_noext = os.path.join(category_html_dir, 'index')
             yield (category_html_path_noext, context, template)
 
             # index in document directory
             document_dir = os.path.dirname(category_html_dir)
-            category_html_path_noext = document_dir + "/index"
-            context["outpath"] = category_html_path_noext + ".html"
+            category_html_path_noext = os.path.join(document_dir, 'index')
+            context['outpath'] = category_html_path_noext + '.html'
             yield (category_html_path_noext, context, template)
 # enddef