diff --git a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
index 049e6f61def2e..8d1695d6603d7 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
@@ -411,8 +411,23 @@ def select_rows(sql, name = nil)
 
       # Executes an INSERT query and returns the new record's ID
       def insert(sql, name = nil, pk = nil, id_value = nil, sequence_name = nil)
-        table = sql.split(" ", 4)[2].gsub('"', '')
-        super || pk && last_insert_id(table, sequence_name || default_sequence_name(table, pk))
+        if insert_id = super
+          insert_id
+        else
+          # Extract the table from the insert sql. Yuck.
+          table = sql.split(" ", 4)[2].gsub('"', '')
+
+          # If neither pk nor sequence name is given, look them up.
+          unless pk || sequence_name
+            pk, sequence_name = *pk_and_sequence_for(table)
+          end
+
+          # If a pk is given, fallback to default sequence name.
+          # Don't fetch last insert id for a table without a pk.
+          if pk && sequence_name ||= default_sequence_name(table, pk)
+            last_insert_id(table, sequence_name)
+          end
+        end
       end
 
       # create a 2D array representing the result set
diff --git a/activerecord/test/cases/database_statements_test.rb b/activerecord/test/cases/database_statements_test.rb
new file mode 100644
index 0000000000000..6274d5250f4e1
--- /dev/null
+++ b/activerecord/test/cases/database_statements_test.rb
@@ -0,0 +1,12 @@
+require "cases/helper"
+
+class DatabaseStatementsTest < ActiveRecord::TestCase
+  def setup
+    @connection = ActiveRecord::Base.connection
+  end
+
+  def test_insert_should_return_the_inserted_id
+    id = @connection.insert("INSERT INTO accounts (firm_id,credit_limit) VALUES (42,5000)")
+    assert_not_nil id
+  end
+end