diff --git a/sasbook/Gemfile.lock b/sasbook/Gemfile.lock
index 5b38263..f7ef9b6 100644
--- a/sasbook/Gemfile.lock
+++ b/sasbook/Gemfile.lock
@@ -42,7 +42,8 @@ GEM
       jekyll (>= 3.3, < 5.0)
     jekyll-watch (2.2.1)
       listen (~> 3.0)
-    kramdown (2.1.0)
+    kramdown (2.3.1)
+      rexml
     kramdown-parser-gfm (1.1.0)
       kramdown (~> 2.0)
     liquid (4.0.3)
@@ -66,6 +67,7 @@ GEM
     rb-fsevent (0.10.3)
     rb-inotify (0.10.0)
       ffi (~> 1.0)
+    rexml (3.2.4)
     rouge (3.11.1)
     safe_yaml (1.0.5)
     sassc (2.2.1)