upgrade pg, appears to be false positive

Gemfile

@@ -145,10 +145,7 @@ gem 'omniauth-github-discourse', require: 'omniauth-github'
 gem 'omniauth-oauth2', require: false
 gem 'omniauth-google-oauth2'
 gem 'oj'
-# pg is downgraded while we investigate a severe memory issu
-#  during multi threading that shows up on 0.18.1
-# This also means we DO NOT work on Ruby 2.2 at the moment
-gem 'pg', '0.15.1'
+gem 'pg'
 gem 'pry-rails', require: false
 gem 'rake'
 

Gemfile.lock

@@ -281,7 +281,7 @@ GEM
     openid-redis-store (0.0.2)
       redis
       ruby-openid
-    pg (0.15.1)
+    pg (0.18.1)
     polyglot (0.3.5)
     progress (3.0.1)
     pry (0.10.1)
@@ -506,7 +506,7 @@ DEPENDENCIES
   omniauth-twitter
   onebox
   openid-redis-store
-  pg (= 0.15.1)
+  pg
   pry-nav
   pry-rails
   puma