diff --git a/.travis.yml b/.travis.yml
index 5aff2941..6256ee85 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -3,7 +3,7 @@ rvm:
 - 2.4.2
 cache: bundler
 install: bundle install
-script: bundle exec middleman build
+script: bundle exec middleman build --verbose
 after_success:
 - tar -cf lrug.org.tar public
 - bzip2 lrug.org.tar
diff --git a/lib/lrug_extended_kramdown.rb b/lib/lrug_extended_kramdown.rb
index 20a8b805..811799e6 100644
--- a/lib/lrug_extended_kramdown.rb
+++ b/lib/lrug_extended_kramdown.rb
@@ -28,6 +28,7 @@ def handle_extension(name, opts, body, type, line_no = nil)
 
   def render_coverage(year, month, talk_id)
     coverage = find_coverage(year, month, talk_id)
+    raise "Missing coverage for #{year}, #{month}, #{talk_id}" if coverage.nil?
     if coverage&.any?
       list = new_block_el(:ol, nil, nil, location: @src.current_line_number)
       list.attr['class'] = 'coverage'