diff --git a/html2doc.gemspec b/html2doc.gemspec
index e4591f4..3ec92b2 100644
--- a/html2doc.gemspec
+++ b/html2doc.gemspec
@@ -32,7 +32,7 @@ Gem::Specification.new do |spec|
   spec.add_dependency "mime-types"
   spec.add_dependency "nokogiri", "~> 1.14"
   spec.add_dependency "plane1converter", "~> 0.0.1"
-  spec.add_dependency "plurimath"
+  spec.add_dependency "plurimath", "~> 0.5.0"
   spec.add_dependency "thread_safe"
   spec.add_dependency "uuidtools"
 
diff --git a/lib/html2doc/version.rb b/lib/html2doc/version.rb
index 113cef3..81eafec 100644
--- a/lib/html2doc/version.rb
+++ b/lib/html2doc/version.rb
@@ -1,3 +1,3 @@
 class Html2Doc
-  VERSION = "1.6.1".freeze
+  VERSION = "1.7.0".freeze
 end