Back to an older acts as taggable

Gemfile

@@ -59,7 +59,8 @@ gem 'geocoder'
 gem 'tinymce-rails'
 gem 'tinymce-rails-langs'
 
-gem 'acts-as-taggable-on'
+# The newer 5th version requires a newer ruby > 2.1
+gem 'acts-as-taggable-on', '< 5'
 gem 'tagsinput-rails'
 
 # SEO optimisations

Gemfile.lock

@@ -72,8 +72,8 @@ GEM
       minitest (~> 5.1)
       thread_safe (~> 0.3, >= 0.3.4)
       tzinfo (~> 1.1)
-    acts-as-taggable-on (5.0.0)
-      activerecord (>= 4.2.8)
+    acts-as-taggable-on (4.0.0)
+      activerecord (>= 4.0)
     addressable (2.5.1)
       public_suffix (~> 2.0, >= 2.0.2)
     arbre (1.1.1)
@@ -432,7 +432,7 @@ PLATFORMS
 DEPENDENCIES
   actionview-encoded_mail_to
   activeadmin!
-  acts-as-taggable-on
+  acts-as-taggable-on (< 5)
   brakeman
   bundler-audit
   byebug