diff --git a/system/Model.php b/system/Model.php
index 751adcb73191..d841d2874fd8 100644
--- a/system/Model.php
+++ b/system/Model.php
@@ -398,7 +398,7 @@ public function first()
 
 		// Some databases, like PostgreSQL, need order
 		// information to consistently return correct results.
-		if (empty($builder->QBOrderBy))
+		if (empty($builder->QBOrderBy) && ! empty($this->primaryKey))
 		{
 			$builder->orderBy($this->table . '.' . $this->primaryKey, 'asc');
 		}
diff --git a/tests/_support/Database/Migrations/20160428212500_Create_test_tables.php b/tests/_support/Database/Migrations/20160428212500_Create_test_tables.php
index 3c84cbbdfd89..8d4a93a0da9c 100644
--- a/tests/_support/Database/Migrations/20160428212500_Create_test_tables.php
+++ b/tests/_support/Database/Migrations/20160428212500_Create_test_tables.php
@@ -85,6 +85,16 @@ public function up()
 		]);
 		$this->forge->addKey('id', true);
 		$this->forge->createTable('empty', true);
+
+		//No Primary Key
+		$this->forge->addField([
+			'key'   => [
+				'type'       => 'VARCHAR',
+				'constraint' => 40,
+			],
+			'value' => ['type' => 'TEXT'],
+		]);
+		$this->forge->createTable('secondary', true);
 	}
 
 	//--------------------------------------------------------------------
@@ -95,6 +105,7 @@ public function down()
 		$this->forge->dropTable('job');
 		$this->forge->dropTable('misc');
 		$this->forge->dropTable('empty');
+		$this->forge->dropTable('secondary');
 	}
 
 	//--------------------------------------------------------------------
diff --git a/tests/_support/Models/SecondaryModel.php b/tests/_support/Models/SecondaryModel.php
new file mode 100644
index 000000000000..19d8228f5f1a
--- /dev/null
+++ b/tests/_support/Models/SecondaryModel.php
@@ -0,0 +1,21 @@
+<?php namespace Tests\Support\Models;
+
+use CodeIgniter\Model;
+
+class SecondaryModel extends Model
+{
+	protected $table = 'secondary';
+
+	protected $primaryKey = null;
+
+	protected $returnType = 'object';
+
+	protected $useSoftDeletes = false;
+
+	protected $dateFormat = 'integer';
+
+	protected $allowedFields = [
+		'key',
+		'value',
+	];
+}
diff --git a/tests/system/Database/Live/ModelTest.php b/tests/system/Database/Live/ModelTest.php
index 7627ed624af1..01418e770287 100644
--- a/tests/system/Database/Live/ModelTest.php
+++ b/tests/system/Database/Live/ModelTest.php
@@ -7,6 +7,7 @@
 use Tests\Support\Models\EntityModel;
 use Tests\Support\Models\EventModel;
 use Tests\Support\Models\JobModel;
+use Tests\Support\Models\SecondaryModel;
 use Tests\Support\Models\SimpleEntity;
 use Tests\Support\Models\UserModel;
 use Tests\Support\Models\ValidModel;
@@ -196,6 +197,25 @@ public function testFirstRespectsSoftDeletes()
 		$this->assertEquals(1, $user->id);
 	}
 
+	public function testFirstWithNoPrimaryKey()
+	{
+		$model = new SecondaryModel();
+
+		$this->db->table('secondary')->insert([
+			'key'   => 'foo',
+			'value' => 'bar',
+		]);
+		$this->db->table('secondary')->insert([
+			'key'   => 'bar',
+			'value' => 'baz',
+		]);
+
+		$record = $model->first();
+
+		$this->assertEquals(1, count($record));
+		$this->assertEquals('foo', $record->key);
+	}
+
 	//--------------------------------------------------------------------
 
 	public function testSaveNewRecordObject()