diff --git a/gemfiles/3.0.gemfile b/gemfiles/3.0.gemfile
index cbaf2ba1..91ccd463 100644
--- a/gemfiles/3.0.gemfile
+++ b/gemfiles/3.0.gemfile
@@ -27,12 +27,7 @@ group :development, :test do
 
   platforms :ruby do
     gem 'sqlite3', '~> 1.2'
-
-    # We would prefer to only constrain mysql2 to '~> 0.3',
-    # but a rails bug (https://github.com/rails/rails/issues/21544)
-    # requires us to constrain to '~> 0.3.20' for now.
-    gem 'mysql2', '~> 0.3.20'
-
+    gem 'mysql2', '~> 0.3.20' # activerecord < 4.2.5 must use mysql2 < 0.4
     gem 'pg', '~> 0.17.1'
   end
 
diff --git a/paper_trail.gemspec b/paper_trail.gemspec
index 46bed657..2b531698 100644
--- a/paper_trail.gemspec
+++ b/paper_trail.gemspec
@@ -43,12 +43,9 @@ Gem::Specification.new do |s|
     s.add_development_dependency 'activerecord-jdbcmysql-adapter', '~> 1.3'
   else
     s.add_development_dependency 'sqlite3', '~> 1.2'
-
-    # We would prefer to only constrain mysql2 to '~> 0.3',
-    # but a rails bug (https://github.com/rails/rails/issues/21544)
-    # requires us to constrain to '~> 0.3.20' for now.
-    s.add_development_dependency 'mysql2', '~> 0.3.20'
-
     s.add_development_dependency 'pg', '~> 0.17'
+
+    # activerecord >= 4.2.5 may use mysql2 >= 0.4
+    s.add_development_dependency 'mysql2', '~> 0.4.2'
   end
 end