diff --git a/requirements_pinned.txt b/requirements_pinned.txt
--- a/requirements_pinned.txt
+++ b/requirements_pinned.txt
@@ -11,6 +11,7 @@ contextlib2==0.6.0.post1
 ecdsa==0.13.2
 gnureadline==6.3.8
 hupper==1.10.2
+mistune==0.8.4
 ipaddress==1.0.23
 importlib-metadata==1.6.0
 jinja2==2.9.6
@@ -25,4 +26,4 @@ tempita==0.5.2
 testpath==0.4.4
 transaction==2.4.0
 vine==1.3.0
-wcwidth==0.1.9
\ No newline at end of file
+wcwidth==0.1.9