diff --git a/lib/generators/acts_as_taggable_on/migration/templates/active_record/migration.rb b/lib/generators/acts_as_taggable_on/migration/templates/active_record/migration.rb
index 16610615f..8add132ad 100644
--- a/lib/generators/acts_as_taggable_on/migration/templates/active_record/migration.rb
+++ b/lib/generators/acts_as_taggable_on/migration/templates/active_record/migration.rb
@@ -12,7 +12,9 @@ def self.up
       t.references :taggable, :polymorphic => true
       t.references :tagger, :polymorphic => true
 
-      t.string :context
+      # limit is created to prevent mysql error o index lenght for myisam table type.
+      # http://bit.ly/vgW2Ql
+      t.string :context, :limit => 128
 
       t.datetime :created_at
     end