diff --git a/src/InputRenderer.php b/src/InputRenderer.php
index a18031f..43361cd 100644
--- a/src/InputRenderer.php
+++ b/src/InputRenderer.php
@@ -148,7 +148,7 @@ class InputRenderer
      * @param string|string[]|null  $collection_name collection name(s) for inputs, e.g. 'myform' or ['myform', '123'] etc.
      * @param string|null           $id_prefix       base id for inputs, e.g. 'myform' or 'myform-123', etc.
      */
-    public function __construct($model = null, $collection_name = null, $id_prefix = null)
+    public function __construct($model = null, $collection_name = null, $id_prefix = "form")
     {
         $this->model = InputModel::create($model);
         $this->collection_name = $collection_name;
diff --git a/tests/unit/FieldRenderCest.php b/tests/unit/FieldRenderCest.php
index 472281d..3321ca5 100644
--- a/tests/unit/FieldRenderCest.php
+++ b/tests/unit/FieldRenderCest.php
@@ -26,38 +26,38 @@ public function renderTextFields(UnitTester $I)
         $model = $form->model;
         $field = new TextField('value');
 
-        $I->assertSame('<input class="form-control" name="value" type="text"/>', $form->render($field),
+        $I->assertSame('<input class="form-control" id="form-value" name="value" type="text"/>', $form->render($field),
             'basic input with no value-attribute');
 
         $field->setValue($model, 'Hello World');
 
-        $I->assertSame('<input class="form-control" name="value" type="text" value="Hello World"/>',
+        $I->assertSame('<input class="form-control" id="form-value" name="value" type="text" value="Hello World"/>',
             $form->render($field), 'basic input with value-attribute');
 
         $field->max_length = 50;
 
-        $I->assertSame('<input class="form-control" maxlength="50" name="value" type="text" value="Hello World"/>',
+        $I->assertSame('<input class="form-control" id="form-value" maxlength="50" name="value" type="text" value="Hello World"/>',
             $form->render($field), 'input with value and maxlength-attribute');
 
         $field->setPlaceholder('hello');
 
-        $I->assertSame('<input class="form-control" maxlength="50" name="value" placeholder="hello" type="text" value="Hello World"/>',
+        $I->assertSame('<input class="form-control" id="form-value" maxlength="50" name="value" placeholder="hello" type="text" value="Hello World"/>',
             $form->render($field), 'input with value, maxlength and placeholder-attributes');
-        $I->assertSame('<input class="form-control" data-foo="bar" maxlength="50" name="value" placeholder="hello" type="text" value="Hello World"/>',
+        $I->assertSame('<input class="form-control" data-foo="bar" id="form-value" maxlength="50" name="value" placeholder="hello" type="text" value="Hello World"/>',
             $form->render($field, ['data-foo' => 'bar']), 'input with custom data-attribute overridden');
-        $I->assertSame('<input class="form-control" maxlength="50" name="value" placeholder="override" type="text" value="Hello World"/>',
+        $I->assertSame('<input class="form-control" id="form-value" maxlength="50" name="value" placeholder="override" type="text" value="Hello World"/>',
             $form->render($field, ['placeholder' => 'override']), 'input with placeholder-attribute overridden');
 
         $field->setValue($model, 'this & that');
 
-        $I->assertSame('<input class="form-control" maxlength="50" name="value" placeholder="hello" type="text" value="this &amp; that"/>',
+        $I->assertSame('<input class="form-control" id="form-value" maxlength="50" name="value" placeholder="hello" type="text" value="this &amp; that"/>',
             $form->render($field), 'input with value-attribute escaped as HTML');
 
         $field = new TextField("value");
 
         $field->setPattern('[A-Z]{2}', 'Enter two-letter ISO language code');
 
-        $I->assertSame('<input class="form-control" data-pattern-error="Enter two-letter ISO language code" name="value" pattern="[A-Z]{2}" type="text" value="this &amp; that"/>',
+        $I->assertSame('<input class="form-control" data-pattern-error="Enter two-letter ISO language code" id="form-value" name="value" pattern="[A-Z]{2}" type="text" value="this &amp; that"/>',
             $form->render($field));
     }
 
@@ -69,7 +69,7 @@ public function renderPasswordField(UnitTester $I)
 
         $field->setValue($model, 'supersecret');
 
-        $I->assertSame('<input class="form-control" name="value" type="password" value=""/>', $form->render($field),
+        $I->assertSame('<input class="form-control" id="form-value" name="value" type="password" value=""/>', $form->render($field),
             'input with type=password');
     }
 
@@ -93,7 +93,7 @@ public function renderEmailField(UnitTester $I)
 
         $field->setValue($model, 'foo@bar.baz');
 
-        $I->assertSame('<input class="form-control" name="value" type="email" value="foo@bar.baz"/>',
+        $I->assertSame('<input class="form-control" id="form-value" name="value" type="email" value="foo@bar.baz"/>',
             $form->render($field), 'input with type=email (html5)');
     }
 
@@ -105,7 +105,7 @@ public function renderTextArea(UnitTester $I)
 
         $field->setValue($model, 'this & that');
 
-        $I->assertSame('<textarea class="form-control" name="value">this &amp; that</textarea>', $form->render($field),
+        $I->assertSame('<textarea class="form-control" id="form-value" name="value">this &amp; that</textarea>', $form->render($field),
             'simple textarea with content');
     }
 
@@ -154,22 +154,22 @@ public function renderSelectTags(UnitTester $I)
             2 => 'Option Two',
         ]);
 
-        $I->assertSame('<select class="form-control" name="value"><option value="1">Option One</option><option value="2">Option Two</option></select>',
+        $I->assertSame('<select class="form-control" id="form-value" name="value"><option value="1">Option One</option><option value="2">Option Two</option></select>',
             $form->render($field));
 
         $field->setValue($form->model, 1);
 
-        $I->assertSame('<select class="form-control" name="value"><option selected value="1">Option One</option><option value="2">Option Two</option></select>',
+        $I->assertSame('<select class="form-control" id="form-value" name="value"><option selected value="1">Option One</option><option value="2">Option Two</option></select>',
             $form->render($field));
 
         $field->disabled = 'Please select';
 
-        $I->assertSame('<select class="form-control" name="value"><option disabled>Please select</option><option selected value="1">Option One</option><option value="2">Option Two</option></select>',
+        $I->assertSame('<select class="form-control" id="form-value" name="value"><option disabled>Please select</option><option selected value="1">Option One</option><option value="2">Option Two</option></select>',
             $form->render($field));
 
         $field->setValue($form->model, null);
 
-        $I->assertSame('<select class="form-control" name="value"><option disabled selected>Please select</option><option value="1">Option One</option><option value="2">Option Two</option></select>',
+        $I->assertSame('<select class="form-control" id="form-value" name="value"><option disabled selected>Please select</option><option value="1">Option One</option><option value="2">Option Two</option></select>',
             $form->render($field));
     }
 
@@ -204,16 +204,16 @@ public function renderIntField(UnitTester $I)
 
         $field = new IntField("value");
 
-        $I->assertSame('<input class="form-control" name="value" pattern="-?\d*" type="number"/>', $form->render($field));
+        $I->assertSame('<input class="form-control" id="form-value" name="value" pattern="-?\d*" type="number"/>', $form->render($field));
 
         $field->min_value = -1;
 
-        $I->assertSame('<input class="form-control" min="-1" name="value" pattern="-?\d*" type="number"/>', $form->render($field));
+        $I->assertSame('<input class="form-control" id="form-value" min="-1" name="value" pattern="-?\d*" type="number"/>', $form->render($field));
 
         $field->min_value = 1;
         $field->max_value = 99;
 
-        $I->assertSame('<input class="form-control" max="99" min="1" name="value" pattern="\d*" type="number"/>', $form->render($field));
+        $I->assertSame('<input class="form-control" id="form-value" max="99" min="1" name="value" pattern="\d*" type="number"/>', $form->render($field));
     }
 
     public function renderFloatField(UnitTester $I)
@@ -222,16 +222,16 @@ public function renderFloatField(UnitTester $I)
 
         $field = new FloatField("value");
 
-        $I->assertSame('<input class="form-control" name="value" pattern="-?\d*(\.(?=\d))?\d*" type="number"/>', $form->render($field));
+        $I->assertSame('<input class="form-control" id="form-value" name="value" pattern="-?\d*(\.(?=\d))?\d*" type="number"/>', $form->render($field));
 
         $field->min_value = -1;
 
-        $I->assertSame('<input class="form-control" min="-1" name="value" pattern="-?\d*(\.(?=\d))?\d*" type="number"/>', $form->render($field));
+        $I->assertSame('<input class="form-control" id="form-value" min="-1" name="value" pattern="-?\d*(\.(?=\d))?\d*" type="number"/>', $form->render($field));
 
         $field->min_value = 1;
         $field->max_value = 99;
 
-        $I->assertSame('<input class="form-control" max="99" min="1" name="value" pattern="\d*(\.(?=\d))?\d*" type="number"/>', $form->render($field));
+        $I->assertSame('<input class="form-control" id="form-value" max="99" min="1" name="value" pattern="\d*(\.(?=\d))?\d*" type="number"/>', $form->render($field));
     }
 
     public function renderDateTimeField(UnitTester $I)
@@ -240,7 +240,7 @@ public function renderDateTimeField(UnitTester $I)
         $field = new DateTimeField('value', 'Europe/Copenhagen', 'Y-m-d H:i:s', ['readonly' => true]);
         $field->setValue($form->model, 173919600);
 
-        $I->assertSame('<input class="form-control" name="value" readonly type="text" value="1975-07-07 00:00:00"/>',
+        $I->assertSame('<input class="form-control" id="form-value" name="value" readonly type="text" value="1975-07-07 00:00:00"/>',
             $form->render($field));
     }
 
@@ -269,17 +269,17 @@ public function renderDateSelector(UnitTester $I)
 
         $I->expectParts(
             $form->render($field), [
-                '<select class="form-control day" name="value[day]">',
+                '<select class="form-control day" id="form-value-day" name="value[day]">',
                 '<option value="1">1</option>',
                 '<option selected value="7">7</option>',
                 '<option value="31">31</option>',
                 '</select>',
-                '<select class="form-control month" name="value[month]">',
+                '<select class="form-control month" id="form-value-month" name="value[month]">',
                 '<option value="1">January</option>',
                 '<option selected value="7">July</option>',
                 '<option value="12">December</option>',
                 '</select>',
-                '<select class="form-control year" name="value[year]">',
+                '<select class="form-control year" id="form-value-year" name="value[year]">',
                 '<option value="1974">1974</option>',
                 '<option selected value="1975">1975</option>',
                 '<option value="1976">1976</option>',
@@ -291,11 +291,11 @@ public function renderDateSelector(UnitTester $I)
 
         $I->expectParts(
             $form->render($field), [
-                '<select class="form-control day" name="value[day]">',
+                '<select class="form-control day" id="form-value-day" name="value[day]">',
                 '<option disabled>Day</option>',
-                '<select class="form-control month" name="value[month]">',
+                '<select class="form-control month" id="form-value-month" name="value[month]">',
                 '<option disabled>Month</option>',
-                '<select class="form-control year" name="value[year]">',
+                '<select class="form-control year" id="form-value-year" name="value[year]">',
                 '<option disabled>Year</option>',
             ]
         );
@@ -304,11 +304,11 @@ public function renderDateSelector(UnitTester $I)
 
         $I->expectParts(
             $form->render($field), [
-                '<select class="form-control day" name="value[day]">',
+                '<select class="form-control day" id="form-value-day" name="value[day]">',
                 '<option disabled selected>Day</option>',
-                '<select class="form-control month" name="value[month]">',
+                '<select class="form-control month" id="form-value-month" name="value[month]">',
                 '<option disabled selected>Month</option>',
-                '<select class="form-control year" name="value[year]">',
+                '<select class="form-control year" id="form-value-year" name="value[year]">',
                 '<option disabled selected>Year</option>',
             ]
         );
diff --git a/tests/unit/InputRendererCest.php b/tests/unit/InputRendererCest.php
index c9693af..fdc481d 100644
--- a/tests/unit/InputRendererCest.php
+++ b/tests/unit/InputRendererCest.php
@@ -15,21 +15,24 @@ public function handleAttributes(UnitTester $I)
         $form = new InputRenderer();
         $field = new TextField('text');
 
-        $I->assertSame('<input class="form-control foo bar" name="text" type="text"/>',
+        $I->assertSame('<input class="form-control foo bar" id="form-text" name="text" type="text"/>',
             $form->render($field, ['class' => ['foo', 'bar']]), 'folds multi-valued class attribute');
-        $I->assertSame('<input class="form-control" name="text" readonly type="text"/>',
+        $I->assertSame('<input class="form-control" id="form-text" name="text" readonly type="text"/>',
             $form->render($field, ['readonly' => true]), 'handles boolean TRUE attribute value');
-        $I->assertSame('<input class="form-control" name="text" type="text"/>',
+        $I->assertSame('<input class="form-control" id="form-text" name="text" type="text"/>',
             $form->render($field, ['readonly' => false]), 'handles boolean FALSE attribute value');
-        $I->assertSame('<input class="form-control" name="text" type="text"/>',
+        $I->assertSame('<input class="form-control" id="form-text" name="text" type="text"/>',
             $form->render($field, ['foo' => null]), 'filters NULL-value attributes');
 
         $form->xhtml = true;
-        $I->assertSame('<input class="form-control" name="text" readonly="readonly" type="text"/>',
+        $I->assertSame('<input class="form-control" id="form-text" name="text" readonly="readonly" type="text"/>',
             $form->render($field, ['readonly' => true]), 'renders value-less attributes as valid XHTML');
         $form->xhtml = false;
 
         $I->assertSame('text', $form->getName($field), 'name without prefix');
+        
+        $form->id_prefix = null;
+        
         $I->assertSame(null, $form->getId($field), 'no id attribute when $id_prefix is NULL');
 
         $form->collection_name = 'form';
@@ -126,7 +129,7 @@ public function renderContainerTags(UnitTester $I)
         $I->assertSame('<div data-foo="bar">foo &amp; bar</div>',
             $form->divFor($field, 'foo &amp; bar', ['data-foo' => 'bar']));
 
-        $I->assertSame('<div data-div="bar"><input class="form-control" data-input="foo" name="text" type="text"/></div>',
+        $I->assertSame('<div data-div="bar"><input class="form-control" data-input="foo" id="form-text" name="text" type="text"/></div>',
             $form->renderDiv($field, ['data-input' => 'foo'], ['data-div' => 'bar']));
 
         $field->setRequired(true);
@@ -136,7 +139,7 @@ public function renderContainerTags(UnitTester $I)
         $I->assertSame('<div class="required has-error" data-foo="bar">foo &amp; bar</div>',
             $form->divFor($field, 'foo &amp; bar', ['data-foo' => 'bar']));
 
-        $I->assertSame('<div class="required has-error foo bar"><input class="form-control foo" name="text" required type="text"/></div>',
+        $I->assertSame('<div class="required has-error foo bar"><input class="form-control foo" id="form-text" name="text" required type="text"/></div>',
             $form->renderDiv($field, ['class' => 'foo'], ['class' => ['foo', 'bar']]));
     }
 
@@ -166,7 +169,7 @@ public function renderInputGroups(UnitTester $I)
 
     public function renderLabelTags(UnitTester $I)
     {
-        $form = new InputRenderer();
+        $form = new InputRenderer(null, null, null);
         $field = new TextField('text');
 
         $I->assertException(
@@ -225,7 +228,7 @@ public function overridePlaceholders(UnitTester $I)
 
         $form->setPlaceholder($field, "Hello");
 
-        $I->assertSame('<input class="form-control" name="test" placeholder="Hello" type="text"/>', $form->render($field));
+        $I->assertSame('<input class="form-control" id="form-test" name="test" placeholder="Hello" type="text"/>', $form->render($field));
     }
 
     public function overrideRequired(UnitTester $I)
@@ -236,7 +239,7 @@ public function overrideRequired(UnitTester $I)
 
         $form->setRequired($field);
 
-        $I->assertSame('<div class="required"><input class="form-control" name="test" required type="text"/></div>', $form->renderDiv($field));
+        $I->assertSame('<div class="required"><input class="form-control" id="form-test" name="test" required type="text"/></div>', $form->renderDiv($field));
     }
 
     public function buildInput(UnitTester $I)