diff --git a/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb b/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
index d3ba3294062731c7cb1611d0a5c68c744c3220e6..4689ac3ac3737c9c97e5f593ac9c84168c6b3ad8 100755
--- a/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
@@ -83,11 +83,15 @@ def self.establish_connection(spec = nil)
         when ConnectionSpecification
           @@defined_connections[self] = spec
         when Symbol, String
-          establish_connection(configurations[spec.to_s])
+          if configuration = configurations[spec.to_s]
+            establish_connection(configuration)
+          else
+            raise AdapterNotSpecified
+          end
         else
           spec = symbolize_strings_in_hash(spec)
           unless spec.key?(:adapter) then raise AdapterNotSpecified end
-    
+
           adapter_method = "#{spec[:adapter]}_connection"
           unless respond_to?(adapter_method) then raise AdapterNotFound end
           remove_connection