diff --git a/requirements.txt b/requirements.txt
index d6a8f90..76760ad 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -32,7 +32,7 @@ sphinx-rtd-theme==2.0.0
 sphinx-tabs==3.4.5
 sphinxcontrib-applehelp==1.0.8
 sphinxcontrib-devhelp==1.0.6
-sphinxcontrib-htmlhelp==2.0.5
+sphinxcontrib-htmlhelp==2.1.0
 sphinxcontrib-jquery==4.1
 sphinxcontrib-jsmath==1.0.1
 sphinxcontrib-qthelp==1.0.7