diff --git a/models/site_file.rb b/models/site_file.rb
index d4eee0b7..afef3139 100644
--- a/models/site_file.rb
+++ b/models/site_file.rb
@@ -81,7 +81,12 @@ class SiteFile < Sequel::Model
       return false, "#{is_directory ? 'directory' : 'file'} already exists"
     end
 
-    unless is_directory
+    if is_directory
+      if new_path.match(/\.html?$/)
+        return false, 'directory name cannot end with .htm or .html'
+      end
+
+    else # a file
       mime_type = Magic.guess_file_mime_type site.files_path(self.path)
       extname = File.extname new_path
 
diff --git a/tests/site_file_tests.rb b/tests/site_file_tests.rb
index 772cc4d5..bc18f4ee 100644
--- a/tests/site_file_tests.rb
+++ b/tests/site_file_tests.rb
@@ -111,6 +111,15 @@ describe 'site_files' do
       # No purge cache is executed because the directory is empty
     end
 
+    it 'fails for directory name ending in .htm or .html' do
+      @site.create_directory 'dirone'
+      dirone = @site.site_files_dataset.where(path: 'dirone').first
+      res = dirone.rename('dasharezone.html')
+      _(res).must_equal [false, 'directory name cannot end with .htm or .html']
+      res = dirone.rename('dasharezone.htm')
+      _(res).must_equal [false, 'directory name cannot end with .htm or .html']
+    end
+
     it 'wont set an empty directory' do
       @site.create_directory 'dirone'
       _(@site.site_files.select {|sf| sf.path == 'dirone'}.length).must_equal 1