diff --git a/src/Command/ModelCommand.php b/src/Command/ModelCommand.php
index 2b006f50..05ebce63 100644
--- a/src/Command/ModelCommand.php
+++ b/src/Command/ModelCommand.php
@@ -984,22 +984,14 @@ public function getRules(Table $model, array $associations, Arguments $args): ar
             return [];
         }
         $schema = $model->getSchema();
-        $fields = $schema->columns();
-        if (empty($fields)) {
+        $schemaFields = $schema->columns();
+        if (empty($schemaFields)) {
             return [];
         }
 
-        $uniqueColumns = ['username', 'login'];
-        if (in_array($model->getAlias(), ['Users', 'Accounts'])) {
-            $uniqueColumns[] = 'email';
-        }
+        $uniqueRules = [];
+        $uniqueConstraintsColumns = [];
 
-        $rules = [];
-        foreach ($fields as $fieldName) {
-            if (in_array($fieldName, $uniqueColumns, true)) {
-                $rules[$fieldName] = ['name' => 'isUnique', 'fields' => [$fieldName], 'options' => []];
-            }
-        }
         foreach ($schema->constraints() as $name) {
             $constraint = $schema->getConstraint($name);
             if ($constraint['type'] !== TableSchema::CONSTRAINT_UNIQUE) {
@@ -1007,8 +999,11 @@ public function getRules(Table $model, array $associations, Arguments $args): ar
             }
 
             $options = [];
-            $fields = $constraint['columns'];
-            foreach ($fields as $field) {
+            /** @var array<string> $constraintFields */
+            $constraintFields = $constraint['columns'];
+            $uniqueConstraintsColumns = [...$uniqueConstraintsColumns, ...$constraintFields];
+
+            foreach ($constraintFields as $field) {
                 if ($schema->isNullable($field)) {
                     $allowMultiple = !ConnectionManager::get($this->connection)->getDriver() instanceof Sqlserver;
                     $options['allowMultipleNulls'] = $allowMultiple;
@@ -1016,15 +1011,37 @@ public function getRules(Table $model, array $associations, Arguments $args): ar
                 }
             }
 
-            $rules[$constraint['columns'][0]] = ['name' => 'isUnique', 'fields' => $fields, 'options' => $options];
+            $uniqueRules[] = ['name' => 'isUnique', 'fields' => $constraintFields, 'options' => $options];
         }
 
+        $possiblyUniqueColumns = ['username', 'login'];
+        if (in_array($model->getAlias(), ['Users', 'Accounts'])) {
+            $possiblyUniqueColumns[] = 'email';
+        }
+
+        $possiblyUniqueRules = [];
+        foreach ($schemaFields as $field) {
+            if (
+                !in_array($field, $uniqueConstraintsColumns, true) &&
+                in_array($field, $possiblyUniqueColumns, true)
+            ) {
+                $possiblyUniqueRules[] = ['name' => 'isUnique', 'fields' => [$field], 'options' => []];
+            }
+        }
+
+        $rules = [...$possiblyUniqueRules, ...$uniqueRules];
+
         if (empty($associations['belongsTo'])) {
             return $rules;
         }
 
         foreach ($associations['belongsTo'] as $assoc) {
-            $rules[$assoc['foreignKey']] = ['name' => 'existsIn', 'extra' => $assoc['alias'], 'options' => []];
+            $rules[] = [
+                'name' => 'existsIn',
+                'fields' => (array)$assoc['foreignKey'],
+                'extra' => $assoc['alias'],
+                'options' => [],
+            ];
         }
 
         return $rules;
diff --git a/templates/bake/Model/table.twig b/templates/bake/Model/table.twig
index 5a1b9620..41a1eb2e 100644
--- a/templates/bake/Model/table.twig
+++ b/templates/bake/Model/table.twig
@@ -128,13 +128,13 @@ class {{ name }}Table extends Table{{ fileBuilder.classBuilder.implements ? ' im
      */
     public function buildRules(RulesChecker $rules): RulesChecker
     {
-{% for field, rule in rulesChecker %}
-{% set fields = rule.fields is defined ? Bake.exportArray(rule.fields) : Bake.exportVar(field) %}
+{% for rule in rulesChecker %}
+{% set fields = Bake.exportArray(rule.fields) %}
 {% set options = '' %}
 {% for optionName, optionValue in rule.options %}
     {%~ set options = (loop.first ? '[' : options) ~ "'#{optionName}' => " ~ Bake.exportVar(optionValue) ~ (loop.last ? ']' : ', ') %}
 {% endfor %}
-        $rules->add($rules->{{ rule.name }}({{ fields|raw }}{{ (rule.extra|default ? ", '#{rule.extra}'" : '')|raw }}{{ (options ? ', ' ~ options : '')|raw }}), ['errorField' => '{{ field }}']);
+        $rules->add($rules->{{ rule.name }}({{ fields|raw }}{{ (rule.extra|default ? ", '#{rule.extra}'" : '')|raw }}{{ (options ? ', ' ~ options : '')|raw }}), ['errorField' => '{{ rule.fields[0] }}']);
 {% endfor %}
 
         return $rules;
diff --git a/tests/TestCase/Command/ModelCommandTest.php b/tests/TestCase/Command/ModelCommandTest.php
index 3e5f8bd9..4a3a8d3b 100644
--- a/tests/TestCase/Command/ModelCommandTest.php
+++ b/tests/TestCase/Command/ModelCommandTest.php
@@ -1368,7 +1368,7 @@ public function testGetRules()
                 ],
                 [
                     'alias' => 'Sites',
-                    'foreignKey' => 'site_id',
+                    'foreignKey' => ['site_id1', 'site_id2'],
                 ],
             ],
             'hasMany' => [
@@ -1382,18 +1382,20 @@ public function testGetRules()
         $args = new Arguments([], [], []);
         $result = $command->getRules($model, $associations, $args);
         $expected = [
-            'username' => [
+            [
                 'name' => 'isUnique',
                 'fields' => ['username'],
                 'options' => [],
             ],
-            'country_id' => [
+            [
                 'name' => 'existsIn',
+                'fields' => ['country_id'],
                 'extra' => 'Countries',
                 'options' => [],
             ],
-            'site_id' => [
+            [
                 'name' => 'existsIn',
+                'fields' => ['site_id1', 'site_id2'],
                 'extra' => 'Sites',
                 'options' => [],
             ],
@@ -1404,9 +1406,6 @@ public function testGetRules()
     /**
      * Tests the getRules with unique keys.
      *
-     * Multi-column constraints are ignored as they would
-     * require a break in compatibility.
-     *
      * @return void
      */
     public function testGetRulesUniqueKeys()
@@ -1416,7 +1415,7 @@ public function testGetRulesUniqueKeys()
             'type' => 'unique',
             'columns' => ['title'],
         ]);
-        $model->getSchema()->addConstraint('ignored_constraint', [
+        $model->getSchema()->addConstraint('unique_composite', [
             'type' => 'unique',
             'columns' => ['title', 'user_id'],
         ]);
@@ -1425,7 +1424,12 @@ public function testGetRulesUniqueKeys()
         $args = new Arguments([], [], []);
         $result = $command->getRules($model, [], $args);
         $expected = [
-            'title' => [
+            [
+                'name' => 'isUnique',
+                'fields' => ['title'],
+                'options' => [],
+            ],
+            [
                 'name' => 'isUnique',
                 'fields' => ['title', 'user_id'],
                 'options' => [],
@@ -1434,6 +1438,124 @@ public function testGetRulesUniqueKeys()
         $this->assertEquals($expected, $result);
     }
 
+    /**
+     * Tests that there are no conflicts between neither multiple constraints,
+     * nor with foreign keys that share one or more identical column.
+     */
+    public function testGetRulesNoColumnNameConflictForUniqueConstraints(): void
+    {
+        $model = $this->getTableLocator()->get('Users');
+        $model->setSchema([
+            'department_id' => ['type' => 'integer', 'null' => false],
+            'username' => ['type' => 'string', 'null' => false],
+            'email' => ['type' => 'string', 'null' => false],
+        ]);
+
+        $model->getSchema()->addConstraint('unique_composite_1', [
+            'type' => 'unique',
+            'columns' => ['department_id', 'username'],
+        ]);
+        $model->getSchema()->addConstraint('unique_composite_2', [
+            'type' => 'unique',
+            'columns' => ['department_id', 'email'],
+        ]);
+
+        $command = new ModelCommand();
+        $args = new Arguments([], [], []);
+        $associations = [
+            'belongsTo' => [
+                ['alias' => 'Departments', 'foreignKey' => 'department_id'],
+            ],
+        ];
+
+        $result = $command->getRules($model, $associations, $args);
+        $expected = [
+            [
+                'name' => 'isUnique',
+                'fields' => ['department_id', 'username'],
+                'options' => [],
+            ],
+            [
+                'name' => 'isUnique',
+                'fields' => ['department_id', 'email'],
+                'options' => [],
+            ],
+            [
+                'name' => 'existsIn',
+                'fields' => ['department_id'],
+                'extra' => 'Departments',
+                'options' => [],
+            ],
+        ];
+        $this->assertEquals($expected, $result);
+    }
+
+    /**
+     * Tests generating unique rules for possibly unique columns based on
+     * column names instead of on actual unique constraints.
+     */
+    public function testGetRulesForPossiblyUniqueColumns(): void
+    {
+        $model = $this->getTableLocator()->get('Users');
+        $model->setSchema([
+            'department_id' => ['type' => 'integer', 'null' => false],
+            'username' => ['type' => 'string', 'null' => false],
+            'login' => ['type' => 'string', 'null' => false],
+            'email' => ['type' => 'string', 'null' => false],
+        ]);
+
+        $command = new ModelCommand();
+        $args = new Arguments([], [], []);
+        $result = $command->getRules($model, [], $args);
+        $expected = [
+            [
+                'name' => 'isUnique',
+                'fields' => ['username'],
+                'options' => [],
+            ],
+            [
+                'name' => 'isUnique',
+                'fields' => ['login'],
+                'options' => [],
+            ],
+            [
+                'name' => 'isUnique',
+                'fields' => ['email'],
+                'options' => [],
+            ],
+        ];
+        $this->assertEquals($expected, $result);
+
+        // possibly unique columns should not cause additional rules
+        // to be generated in case the column is already present in
+        // an actual unique constraint
+
+        $model->getSchema()->addConstraint('unique_composite', [
+            'type' => 'unique',
+            'columns' => ['department_id', 'username'],
+        ]);
+
+        $result = $command->getRules($model, [], $args);
+        $expected = [
+            [
+                'name' => 'isUnique',
+                'fields' => ['login'],
+                'options' => [],
+            ],
+            [
+                'name' => 'isUnique',
+                'fields' => ['email'],
+                'options' => [],
+            ],
+            [
+                'name' => 'isUnique',
+                'fields' => ['department_id', 'username'],
+                'options' => [],
+            ],
+        ];
+        $this->assertEquals($expected, $result);
+    }
+
     /**
      * Test that specific behaviors are auto-detected
      *
diff --git a/tests/comparisons/Model/testBakeAssociationDetectionCategoriesProductsTable.php b/tests/comparisons/Model/testBakeAssociationDetectionCategoriesProductsTable.php
index d1f7d554..c5fff2bf 100644
--- a/tests/comparisons/Model/testBakeAssociationDetectionCategoriesProductsTable.php
+++ b/tests/comparisons/Model/testBakeAssociationDetectionCategoriesProductsTable.php
@@ -63,8 +63,8 @@ public function initialize(array $config): void
      */
     public function buildRules(RulesChecker $rules): RulesChecker
     {
-        $rules->add($rules->existsIn('category_id', 'Categories'), ['errorField' => 'category_id']);
-        $rules->add($rules->existsIn('product_id', 'Products'), ['errorField' => 'product_id']);
+        $rules->add($rules->existsIn(['category_id'], 'Categories'), ['errorField' => 'category_id']);
+        $rules->add($rules->existsIn(['product_id'], 'Products'), ['errorField' => 'product_id']);
 
         return $rules;
     }
diff --git a/tests/comparisons/Model/testBakeAssociationDetectionProductVersionsTable.php b/tests/comparisons/Model/testBakeAssociationDetectionProductVersionsTable.php
index c4c27056..c6723816 100644
--- a/tests/comparisons/Model/testBakeAssociationDetectionProductVersionsTable.php
+++ b/tests/comparisons/Model/testBakeAssociationDetectionProductVersionsTable.php
@@ -78,7 +78,7 @@ public function validationDefault(Validator $validator): Validator
      */
     public function buildRules(RulesChecker $rules): RulesChecker
     {
-        $rules->add($rules->existsIn('product_id', 'Products'), ['errorField' => 'product_id']);
+        $rules->add($rules->existsIn(['product_id'], 'Products'), ['errorField' => 'product_id']);
 
         return $rules;
     }
diff --git a/tests/comparisons/Model/testBakeAssociationDetectionProductVersionsTableSigned.php b/tests/comparisons/Model/testBakeAssociationDetectionProductVersionsTableSigned.php
index 3e07ce94..9e3a4a62 100644
--- a/tests/comparisons/Model/testBakeAssociationDetectionProductVersionsTableSigned.php
+++ b/tests/comparisons/Model/testBakeAssociationDetectionProductVersionsTableSigned.php
@@ -78,7 +78,7 @@ public function validationDefault(Validator $validator): Validator
      */
     public function buildRules(RulesChecker $rules): RulesChecker
     {
-        $rules->add($rules->existsIn('product_id', 'Products'), ['errorField' => 'product_id']);
+        $rules->add($rules->existsIn(['product_id'], 'Products'), ['errorField' => 'product_id']);
 
         return $rules;
     }
diff --git a/tests/comparisons/Model/testBakeTableConfig.php b/tests/comparisons/Model/testBakeTableConfig.php
index a27066c3..16309d95 100644
--- a/tests/comparisons/Model/testBakeTableConfig.php
+++ b/tests/comparisons/Model/testBakeTableConfig.php
@@ -113,7 +113,7 @@ public function validationDefault(Validator $validator): Validator
      */
     public function buildRules(RulesChecker $rules): RulesChecker
     {
-        $rules->add($rules->existsIn('user_id', 'Users'), ['errorField' => 'user_id']);
+        $rules->add($rules->existsIn(['user_id'], 'Users'), ['errorField' => 'user_id']);
 
         return $rules;
     }
diff --git a/tests/comparisons/Model/testBakeTableWithCounterCache.php b/tests/comparisons/Model/testBakeTableWithCounterCache.php
index 5ed0a531..7e5369e0 100644
--- a/tests/comparisons/Model/testBakeTableWithCounterCache.php
+++ b/tests/comparisons/Model/testBakeTableWithCounterCache.php
@@ -66,7 +66,7 @@ public function initialize(array $config): void
      */
     public function buildRules(RulesChecker $rules): RulesChecker
     {
-        $rules->add($rules->existsIn('todo_item_id', 'TodoItems'), ['errorField' => 'todo_item_id']);
+        $rules->add($rules->existsIn(['todo_item_id'], 'TodoItems'), ['errorField' => 'todo_item_id']);
 
         return $rules;
     }
diff --git a/tests/comparisons/Model/testBakeUpdateTableNoFile.php b/tests/comparisons/Model/testBakeUpdateTableNoFile.php
index 5b037c52..0d262638 100644
--- a/tests/comparisons/Model/testBakeUpdateTableNoFile.php
+++ b/tests/comparisons/Model/testBakeUpdateTableNoFile.php
@@ -113,7 +113,7 @@ public function validationDefault(Validator $validator): Validator
      */
     public function buildRules(RulesChecker $rules): RulesChecker
     {
-        $rules->add($rules->existsIn('user_id', 'Users'), ['errorField' => 'user_id']);
+        $rules->add($rules->existsIn(['user_id'], 'Users'), ['errorField' => 'user_id']);
 
         return $rules;
     }