diff --git a/Gemfile b/Gemfile
index 5077c257d9..75a917e9cf 100644
--- a/Gemfile
+++ b/Gemfile
@@ -42,7 +42,7 @@ gem "json", ">= 2.0.0"
 gem "rubocop", ">= 0.47", require: false
 
 group :doc do
-  gem "sdoc", "1.0.0.rc1"
+  gem "sdoc", "> 1.0.0.rc1", "< 2.0"
   gem "redcarpet", "~> 3.2.3", platforms: :ruby
   gem "w3c_validators"
   gem "kindlerb", "~> 1.2.0"
diff --git a/Gemfile.lock b/Gemfile.lock
index da7e5a8cab..445bab1ca3 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -264,7 +264,7 @@ GEM
     rainbow (2.2.1)
     rake (12.0.0)
     rb-fsevent (0.9.8)
-    rdoc (5.0.0)
+    rdoc (5.1.0)
     redcarpet (3.2.3)
     redis (3.3.2)
     redis-namespace (1.5.2)
@@ -298,8 +298,8 @@ GEM
       sprockets (>= 2.8, < 4.0)
       sprockets-rails (>= 2.0, < 4.0)
       tilt (>= 1.1, < 3)
-    sdoc (1.0.0.rc1)
-      rdoc (= 5.0.0)
+    sdoc (1.0.0.rc2)
+      rdoc (~> 5.0)
     selenium-webdriver (3.0.5)
       childprocess (~> 0.5)
       rubyzip (~> 1.0)
@@ -417,7 +417,7 @@ DEPENDENCIES
   resque-scheduler
   rubocop (>= 0.47)
   sass-rails
-  sdoc (= 1.0.0.rc1)
+  sdoc (> 1.0.0.rc1, < 2.0)
   sequel
   sidekiq
   sneakers