diff --git a/src/Compat/FilterProcessor.php b/src/Compat/FilterProcessor.php
index 7956898..93f6b94 100644
--- a/src/Compat/FilterProcessor.php
+++ b/src/Compat/FilterProcessor.php
@@ -328,6 +328,12 @@ protected function requireAndResolveFilterColumns(Filter\Rule $filter, Query $qu
 
                         $subQuerySelect->having(["COUNT(DISTINCT $targetKeys) >= ?" => $count]);
                         $subQuerySelect->groupBy(array_values($subQuerySelect->getColumns()));
+
+                        if ($negate) {
+                            $subQuerySelect->where(array_map(function ($k) {
+                                return $k . ' IS NOT NULL';
+                            }, array_values($subQuerySelect->getColumns())));
+                        }
                     }
 
                     // TODO: Qualification is only necessary since the `In` and `NotIn` conditions are ignored by
diff --git a/tests/FilterProcessorTest.php b/tests/FilterProcessorTest.php
index c80c0c1..e91c2a6 100644
--- a/tests/FilterProcessorTest.php
+++ b/tests/FilterProcessorTest.php
@@ -4,10 +4,15 @@
 
 use ipl\Orm\Compat\FilterProcessor;
 use ipl\Orm\Query;
+use ipl\Sql\Connection;
+use ipl\Sql\Test\Databases;
 use ipl\Stdlib\Filter;
+use ipl\Tests\Orm\Lib\Model\Office;
 
 class FilterProcessorTest extends \PHPUnit\Framework\TestCase
 {
+    use Databases;
+
     public function testUnequalDoesNotOverrideUnlike()
     {
         $query = new Query();
@@ -39,6 +44,9 @@ public function testUnequalDoesNotOverrideUnlike()
                             ]]
                         ]]
                     ]]
+                ]],
+                ['AND', [
+                    'sub_passenger_car.id IS NOT NULL'
                 ]]
             ]],
             $where[1][0][1][0][1]['(car.id NOT IN (?) OR car.id IS NULL)']->getWhere()
@@ -57,9 +65,71 @@ public function testUnequalDoesNotOverrideUnlike()
                             ]]
                         ]]
                     ]]
+                ]],
+                ['AND', [
+                    'sub_passenger_car.id IS NOT NULL'
                 ]]
             ]],
             $where[1][0][1][1][1]['(car.id NOT IN (?) OR car.id IS NULL)']->getWhere()
         );
     }
+
+    /**
+     * Test whether an unequal, that targets a to-many relation to which a link can only be established through an
+     * optional other relation, is built by the ORM in a way that coincidental matches are ignored
+     *
+     * This will fail if the ORM generates a NOT IN which uses a subquery that produces NULL values.
+     *
+     * @dataProvider databases
+     */
+    public function testUnequalTargetingAnOptionalToManyRelationIgnoresFalsePositives(Connection $db)
+    {
+        $db->insert('office', ['id' => 1, 'city' => 'London']);
+        $db->insert('department', ['id' => 1, 'name' => 'Accounting']);
+        $db->insert('department', ['id' => 2, 'name' => 'Kitchen']);
+        $db->insert('employee', ['id' => 1, 'department_id' => 1, 'name' => 'Minnie', 'role' => 'CEO']); // remote
+        $db->insert(
+            'employee',
+            ['id' => 2, 'department_id' => 2, 'office_id' => 1, 'name' => 'Goofy', 'role' => 'Developer']
+        );
+
+        // This POC uses inner joins to achieve the desired result
+        $offices = $db->prepexec(
+            'SELECT office.city FROM office'
+            . ' INNER JOIN employee e on e.office_id = office.id'
+            . ' INNER JOIN department d on e.department_id = d.id'
+            . ' WHERE d.name != ?'
+            . ' GROUP BY office.id'
+            . ' ORDER BY office.id',
+            ['Accounting']
+        )->fetchAll();
+
+        $this->assertSame('London', $offices[0]['city'] ?? 'not found');
+
+        // The ORM will use a NOT IN and needs to ignore false positives explicitly
+        $offices = Office::on($db)
+            ->columns(['office.city'])
+            ->orderBy('office.id')
+            ->filter(Filter::unequal('employee.department.name', 'Accounting'));
+        $results = iterator_to_array($offices);
+
+        $this->assertSame('London', $results[0]['city'] ?? 'not found');
+    }
+
+    protected function createSchema(Connection $db, string $driver): void
+    {
+        $db->exec('CREATE TABLE office (id INT PRIMARY KEY, city VARCHAR(255))');
+        $db->exec('CREATE TABLE department (id INT PRIMARY KEY, name VARCHAR(255))');
+        $db->exec(
+            'CREATE TABLE employee (id INT PRIMARY KEY, department_id INT,'
+            . ' office_id INT, name VARCHAR(255), role VARCHAR(255))'
+        );
+    }
+
+    protected function dropSchema(Connection $db, string $driver): void
+    {
+        $db->exec('DROP TABLE IF EXISTS employee');
+        $db->exec('DROP TABLE IF EXISTS department');
+        $db->exec('DROP TABLE IF EXISTS office');
+    }
 }
diff --git a/tests/Lib/Model/Department.php b/tests/Lib/Model/Department.php
new file mode 100644
index 0000000..167c5ae
--- /dev/null
+++ b/tests/Lib/Model/Department.php
@@ -0,0 +1,32 @@
+<?php
+
+namespace ipl\Tests\Orm\Lib\Model;
+
+use ipl\Orm\Model;
+use ipl\Orm\Relations;
+
+class Department extends Model
+{
+    public function getTableName()
+    {
+        return 'department';
+    }
+
+    public function getKeyName()
+    {
+        return 'id';
+    }
+
+    public function getColumns()
+    {
+        return [
+            'name'
+        ];
+    }
+
+    public function createRelations(Relations $relations)
+    {
+        $relations->hasMany('employee', Employee::class)
+            ->setJoinType('LEFT');
+    }
+}
diff --git a/tests/Lib/Model/Employee.php b/tests/Lib/Model/Employee.php
new file mode 100644
index 0000000..8ee65c0
--- /dev/null
+++ b/tests/Lib/Model/Employee.php
@@ -0,0 +1,36 @@
+<?php
+
+namespace ipl\Tests\Orm\Lib\Model;
+
+use ipl\Orm\Model;
+use ipl\Orm\Relations;
+
+class Employee extends Model
+{
+    public function getTableName()
+    {
+        return 'employee';
+    }
+
+    public function getKeyName()
+    {
+        return 'id';
+    }
+
+    public function getColumns()
+    {
+        return [
+            'name',
+            'role',
+            'department_id',
+            'office_id'
+        ];
+    }
+
+    public function createRelations(Relations $relations)
+    {
+        $relations->belongsTo('department', Department::class);
+        $relations->belongsTo('office', Office::class)
+            ->setJoinType('LEFT');
+    }
+}
diff --git a/tests/Lib/Model/Office.php b/tests/Lib/Model/Office.php
new file mode 100644
index 0000000..9228f13
--- /dev/null
+++ b/tests/Lib/Model/Office.php
@@ -0,0 +1,31 @@
+<?php
+
+namespace ipl\Tests\Orm\Lib\Model;
+
+use ipl\Orm\Model;
+use ipl\Orm\Relations;
+
+class Office extends Model
+{
+    public function getTableName()
+    {
+        return 'office';
+    }
+
+    public function getKeyName()
+    {
+        return 'id';
+    }
+
+    public function getColumns()
+    {
+        return [
+            'city'
+        ];
+    }
+
+    public function createRelations(Relations $relations)
+    {
+        $relations->hasMany('employee', Employee::class);
+    }
+}