diff --git a/README.md b/README.md
index 44dca17..9c13f56 100755
--- a/README.md
+++ b/README.md
@@ -43,6 +43,7 @@ Write a graph to a file:
 
 ## Dependencies
 * [RDF.rb](https://rubygems.org/gems/rdf) (~> 3.2)
+* [Haml](https://rubygems.org/gems/haml) (~>- 5.2)
 * Soft dependency on [Nokogiri](https://rubygems.org/gems/nokogiri) (>= 1.12)
 
 ## Documentation
diff --git a/rdf-rdfxml.gemspec b/rdf-rdfxml.gemspec
index c399f48..586b641 100755
--- a/rdf-rdfxml.gemspec
+++ b/rdf-rdfxml.gemspec
@@ -32,6 +32,7 @@ Gem::Specification.new do |gem|
   gem.add_runtime_dependency     'rdf-xsd',         '~> 3.2'
   gem.add_runtime_dependency     'rdf-rdfa',        '~> 3.2'
   gem.add_runtime_dependency     'htmlentities',    '~> 4.3'
+  gem.add_runtime_dependency     'haml',            '~> 5.2' # Until workaround for haml_tag is found.
 
   gem.add_development_dependency 'json-ld',         '>= 3.2'
   gem.add_development_dependency 'rspec',           '~> 3.10'