1 files changed, 4 insertions, 0 deletions
diff --git a/activerecord/lib/active_record/tasks/database_tasks.rb b/activerecord/lib/active_record/tasks/database_tasks.rb
index 67c7e714e6..4fa7cf8a7d 100644
--- a/activerecord/lib/active_record/tasks/database_tasks.rb
+++ b/activerecord/lib/active_record/tasks/database_tasks.rb
@@ -1,6 +1,7 @@
 module ActiveRecord
   module Tasks # :nodoc:
     class DatabaseAlreadyExists < StandardError; end # :nodoc:
+    class DatabaseNotSupported < StandardError; end # :nodoc:
 
     module DatabaseTasks # :nodoc:
       extend self
@@ -121,6 +122,9 @@ module ActiveRecord
 
       def class_for_adapter(adapter)
         key = @tasks.keys.detect { |pattern| adapter[pattern] }
+        unless key
+          raise DatabaseNotSupported, "Rake tasks not supported by '#{adapter}' adapter"
+        end
         @tasks[key]
       end