diff --git a/Gemfile b/Gemfile
index d01ba82af..d0b03a576 100644
--- a/Gemfile
+++ b/Gemfile
@@ -16,7 +16,9 @@ gem "aws-sdk-s3" # Using in Shrine
 gem "browser", require: "browser/browser"
 gem "by_star"
 gem "cld"
-gem "commonmarker" # Using github-markup
+# github-markupが1系に対応するまで0系を使う
+# ref: https://github.com/github/markup/issues/1758
+gem "commonmarker", "< 1.0" # Using github-markup
 gem "counter_culture"
 gem "cssbundling-rails"
 gem "delayed_job_active_record"
diff --git a/Gemfile.lock b/Gemfile.lock
index e741db9ea..1a62ee664 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -144,8 +144,7 @@ GEM
     coderay (1.1.3)
     coercible (1.0.0)
       descendants_tracker (~> 0.0.1)
-    commonmarker (1.0.4)
-      rb_sys (~> 0.9)
+    commonmarker (0.23.10)
     concurrent-ruby (1.2.3)
     connection_pool (2.3.0)
     content_disposition (1.0.0)
@@ -456,7 +455,6 @@ GEM
     rb-fsevent (0.11.1)
     rb-inotify (0.10.1)
       ffi (~> 1.0)
-    rb_sys (0.9.90)
     redis (5.0.5)
       redis-client (>= 0.9.0)
     redis-client (0.9.0)
@@ -619,7 +617,7 @@ DEPENDENCIES
   bullet
   by_star
   cld
-  commonmarker
+  commonmarker (< 1.0)
   counter_culture
   cssbundling-rails
   delayed_job_active_record