diff --git a/Gemfile.lock b/Gemfile.lock
index 07ce155..d358006 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -55,7 +55,8 @@ GEM
     regexp_parser (2.9.0)
     reverse_markdown (2.1.1)
       nokogiri
-    rexml (3.2.6)
+    rexml (3.3.3)
+      strscan
     rspec (3.12.0)
       rspec-core (~> 3.12.0)
       rspec-expectations (~> 3.12.0)
@@ -115,6 +116,7 @@ GEM
       thor (~> 1.0)
       tilt (~> 2.0)
       yard (~> 0.9, >= 0.9.24)
+    strscan (3.1.0)
     syntax_tree (6.2.0)
       prettier_print (>= 1.2.0)
     syntax_tree-haml (4.0.3)