diff --git a/src/php/access/AbstractAccess.php b/src/php/access/AbstractAccess.php
index fb51207..d90ad7f 100644
--- a/src/php/access/AbstractAccess.php
+++ b/src/php/access/AbstractAccess.php
@@ -49,7 +49,10 @@ abstract class AbstractAccess implements IAccess {
   function ensureAssoc(array $keys, ?array $params=null): void {
   }
 
-  function ensureKeys(array $defaults, ?array $params=null): void {
+  function ensureKeys(array $defaults, ?array $missings, ?array $params=null): void {
+  }
+
+  function deleteMissings(array $missings, ?array $params=null): void {
   }
 
   function ensureOrder(array $keys, ?array $params=null): void {
diff --git a/src/php/access/ChainAccess.php b/src/php/access/ChainAccess.php
index 3ed339e..6395d99 100644
--- a/src/php/access/ChainAccess.php
+++ b/src/php/access/ChainAccess.php
@@ -170,7 +170,7 @@ class ChainAccess extends AbstractAccess {
     #$this->access->ensureAssoc($keys, $params);
   }
 
-  function ensureKeys(array $defaults, ?array $params=null): void {
+  function ensureKeys(array $defaults, ?array $missings, ?array $params=null): void {
     #XXX fonction de $accessType?
     #$this->access->ensureKeys($defaults, $params);
   }
diff --git a/src/php/access/IAccess.php b/src/php/access/IAccess.php
index b81692b..71d8631 100644
--- a/src/php/access/IAccess.php
+++ b/src/php/access/IAccess.php
@@ -39,10 +39,16 @@ interface IAccess extends IGetter, ISetter, IDeleter {
 
   /**
    * s'assurer que toutes les clés mentionnées dans le tableau $defaults
-   * existent. si elles n'existent pas, leur donner la valeur du tableau
-   * $defaults
+   * existent. si elles n'existent pas, ou si elles ont la valeur correspondante
+   * du tableau $missings, leur donner la valeur du tableau $defaults
    */
-  function ensureKeys(array $defaults, ?array $params=null): void;
+  function ensureKeys(array $defaults, ?array $missings, ?array $params=null): void;
+
+  /**
+   * supprimer toutes les clés dont la valeur est celle mentionnée dans le
+   * tableau $missings
+   */
+  function deleteMissings(array $missings, ?array $params=null): void;
 
   /**
    * s'assure que les clés de la destination sont dans l'ordre mentionné dans le
diff --git a/src/php/access/KeyAccess.php b/src/php/access/KeyAccess.php
index 47a8291..fbc9781 100644
--- a/src/php/access/KeyAccess.php
+++ b/src/php/access/KeyAccess.php
@@ -142,15 +142,30 @@ class KeyAccess extends AbstractAccess {
     }
   }
 
-  function ensureKeys(array $defaults, ?array $params=null): void {
+  function ensureKeys(array $defaults, ?array $missings, ?array $params=null): void {
     $dest =& $this->dest;
     $keys = array_keys($defaults);
     $prefix = $params["key_prefix"] ?? null;
     $suffix = $params["key_suffix"] ?? null;
     foreach ($keys as $key) {
       $destKey = "$prefix$key$suffix";
+      $haveMissing = $missings !== null && array_key_exists($key, $missings);
       if ($dest === null || !array_key_exists($destKey, $dest)) {
         $dest[$destKey] = $defaults[$key];
+      } elseif ($haveMissing && $dest[$destKey] === $missings[$key]) {
+        $dest[$destKey] = $defaults[$key];
+      }
+    }
+  }
+
+  function deleteMissings(array $missings, ?array $params=null): void {
+    $dest =& $this->dest;
+    $prefix = $params["key_prefix"] ?? null;
+    $suffix = $params["key_suffix"] ?? null;
+    foreach ($missings as $key => $missing) {
+      $destKey = "$prefix$key$suffix";
+      if (array_key_exists($destKey, $dest) && $dest[$destKey] === $missing) {
+        unset($dest[$destKey]);
       }
     }
   }
diff --git a/src/php/access/PropertyAccess.php b/src/php/access/PropertyAccess.php
index c91529b..b0bc011 100644
--- a/src/php/access/PropertyAccess.php
+++ b/src/php/access/PropertyAccess.php
@@ -144,7 +144,7 @@ class PropertyAccess extends AbstractAccess {
     return new ChainAccess($this, $key);
   }
 
-  function ensureKeys(array $defaults, ?array $params=null): void {
+  function ensureKeys(array $defaults, ?array $missings, ?array $params=null): void {
     $dest = $this->dest;
     if ($dest === null) {
       # comme ne connait pas la classe de l'objet destination, on n'essaie pas
diff --git a/src/php/access/ShadowAccess.php b/src/php/access/ShadowAccess.php
index 639b311..accb960 100644
--- a/src/php/access/ShadowAccess.php
+++ b/src/php/access/ShadowAccess.php
@@ -62,8 +62,8 @@ class ShadowAccess extends AbstractAccess {
     $this->writer->ensureAssoc($keys, $params);
   }
 
-  function ensureKeys(array $defaults, ?array $params=null): void {
-    $this->writer->ensureKeys($defaults, $params);
+  function ensureKeys(array $defaults, ?array $missings, ?array $params=null): void {
+    $this->writer->ensureKeys($defaults, $missings, $params);
   }
 
   function ensureOrder(array $keys, ?array $params=null): void {
diff --git a/src/schema/Wrapper.php b/src/schema/Wrapper.php
index 425e0f6..12049c0 100644
--- a/src/schema/Wrapper.php
+++ b/src/schema/Wrapper.php
@@ -149,6 +149,11 @@ abstract class Wrapper implements ArrayAccess, IteratorAggregate {
     return $this->getResult($key)->available;
   }
 
+  /** retourner true si la valeur est nulle */
+  function isNull($key=false): bool {
+    return $this->getResult($key)->null;
+  }
+
   /** retourner true si la valeur est valide */
   function isValid($key=false): bool {
     return $this->getResult($key)->valid;
diff --git a/src/schema/_assoc/AssocWrapper.php b/src/schema/_assoc/AssocWrapper.php
index 9d33c7f..2b77804 100644
--- a/src/schema/_assoc/AssocWrapper.php
+++ b/src/schema/_assoc/AssocWrapper.php
@@ -102,16 +102,39 @@ class AssocWrapper extends Wrapper {
     $result = $context->result;
     if (!$result->valid) return $what;
 
+    $schema = $context->schema;
+    $keys = $schema->getKeys();
+    $defaults = [];
+    $missings = null;
+    foreach ($keys as $key) {
+      $type = $wrapper->getType($key);
+      $default = $schema->getSchema($key)->default;
+      if ($default === null) $default = $type->getNullValue();
+      $defaults[$key] = $default;
+      $missing = $type->getMissingValue($valid);
+      if ($valid) $missings[$key] = $missing;
+    }
+
     foreach ($context->keyWrappers as $keyWrapper) {
       $keyWrapper->analyze($params);
-      if (!$keyWrapper->isValid()) {
-        #XXX distinguer MISSING, UNAVAILABLE, NULL et !VALID
-        $what = ref_analyze::INVALID;
+      if ($keyWrapper->isValid()) continue;
+      $what = ref_analyze::INVALID;
+      if (!$keyWrapper->isPresent()) {
+        $result->addMissingMessage($keyWrapper);
+      } elseif (!$keyWrapper->isAvailable()) {
+        $result->addUnavailableMessage($keyWrapper);
+      } elseif ($keyWrapper->isNull()) {
+        $result->addNullMessage($keyWrapper);
+      } else {
         $result->addInvalidMessage($keyWrapper);
       }
     }
+    if ($params["ensure_keys"] ?? $context->ensureKeys) {
+      $context->input->ensureKeys($defaults, $missings, $params);
+    } else {
+      $context->input->deleteMissings($missings, $params);
+    }
 
-    #XXX supprimer les clés "missing" ou "unavailable" sauf si $ensureKeys
     return $what;
   }
 
@@ -120,23 +143,11 @@ class AssocWrapper extends Wrapper {
    * @param AssocWrapper $wrapper
    */
   static function _normalize(WrapperContext $context, Wrapper $wrapper, ?array $params): bool {
-    $ensureKeys = $params["ensure_keys"] ?? $context->ensureKeys;
     $ensureOrder = $params["ensure_order"] ?? $context->ensureOrder;
-    if ($ensureKeys || $ensureOrder) {
+    if ($ensureOrder) {
       $schema = $context->schema;
       $keys = $schema->getKeys();
-      if ($ensureKeys) {
-        $defaults = [];
-        foreach ($keys as $key) {
-          $default = $schema->getSchema($key)->default;
-          if ($default === null) {
-            $default = $wrapper->getType($key)->getNullValue();
-          }
-          $defaults[$key] = $default;
-        }
-      }
-      if ($ensureKeys) $context->input->ensureKeys($defaults, $params);
-      if ($ensureOrder) $context->input->ensureOrder($keys, $params);
+      $context->input->ensureOrder($keys, $params);
     }
 
     $modified = ScalarWrapper::_normalize($context, $wrapper, $params);
diff --git a/src/schema/_scalar/ScalarResult.php b/src/schema/_scalar/ScalarResult.php
index c442bdb..b538444 100644
--- a/src/schema/_scalar/ScalarResult.php
+++ b/src/schema/_scalar/ScalarResult.php
@@ -67,6 +67,29 @@ class ScalarResult extends Result {
     }
   }
 
+  function addMissingMessage(Wrapper $wrapper): void {
+    $this->resultAvailable = true;
+    $this->present = false;
+    $this->available = false;
+    $this->null = false;
+    $this->valid = false;
+    $this->messageKey = "missing";
+    $result = $wrapper->getResult();
+    $resultException = $result->exception;
+    $resultMessage = $result->message;
+    if ($resultException !== null) {
+      $tmessage = ValueException::get_message($resultException);
+      if ($tmessage) {
+        if ($resultMessage !== null) $resultMessage .= ": ";
+        $resultMessage .= $tmessage;
+      }
+    }
+    $message = $this->message;
+    if ($message) $message .= "\n";
+    $message .= $resultMessage;
+    $this->message = $message;
+  }
+
   function setUnavailable( Schema $schema): int {
     $this->resultAvailable = true;
     $this->present = true;
@@ -83,6 +106,29 @@ class ScalarResult extends Result {
     }
   }
 
+  function addUnavailableMessage(Wrapper $wrapper): void {
+    $this->resultAvailable = true;
+    $this->present = true;
+    $this->available = false;
+    $this->null = false;
+    $this->valid = false;
+    $this->messageKey = "unavailable";
+    $result = $wrapper->getResult();
+    $resultException = $result->exception;
+    $resultMessage = $result->message;
+    if ($resultException !== null) {
+      $tmessage = ValueException::get_message($resultException);
+      if ($tmessage) {
+        if ($resultMessage !== null) $resultMessage .= ": ";
+        $resultMessage .= $tmessage;
+      }
+    }
+    $message = $this->message;
+    if ($message) $message .= "\n";
+    $message .= $resultMessage;
+    $this->message = $message;
+  }
+
   function setNull( Schema $schema): int {
     $this->resultAvailable = true;
     $this->present = true;
@@ -99,6 +145,29 @@ class ScalarResult extends Result {
     }
   }
 
+  function addNullMessage(Wrapper $wrapper): void {
+    $this->resultAvailable = true;
+    $this->present = true;
+    $this->available = true;
+    $this->null = true;
+    $this->valid = false;
+    $this->messageKey = "null";
+    $result = $wrapper->getResult();
+    $resultException = $result->exception;
+    $resultMessage = $result->message;
+    if ($resultException !== null) {
+      $tmessage = ValueException::get_message($resultException);
+      if ($tmessage) {
+        if ($resultMessage !== null) $resultMessage .= ": ";
+        $resultMessage .= $tmessage;
+      }
+    }
+    $message = $this->message;
+    if ($message) $message .= "\n";
+    $message .= $resultMessage;
+    $this->message = $message;
+  }
+
   function setInvalid($value,  Schema $schema, ?Throwable $exception=null): int {
     $this->resultAvailable = true;
     $this->present = true;
diff --git a/src/schema/_scalar/ScalarWrapper.php b/src/schema/_scalar/ScalarWrapper.php
index 1f43f4b..72f1e40 100644
--- a/src/schema/_scalar/ScalarWrapper.php
+++ b/src/schema/_scalar/ScalarWrapper.php
@@ -124,6 +124,16 @@ class ScalarWrapper extends Wrapper {
     }
 
     $value = $input->get($valueKey);
+    $missing = $type->getMissingValue($haveMissing);
+    if ($haveMissing && $value === $missing) {
+      if ($default !== null) {
+        $input->set($default, $valueKey);
+        return $result->setNormalized();
+      } else {
+        return $result->setMissing($schema);
+      }
+    }
+
     $context->origValue = $context->value = $value;
     if ($type->isNull($value)) {
       return $result->setNull($schema);
diff --git a/src/schema/input/Input.php b/src/schema/input/Input.php
index 59eefaa..4935bd6 100644
--- a/src/schema/input/Input.php
+++ b/src/schema/input/Input.php
@@ -76,8 +76,12 @@ class Input {
     $this->access->ensureAssoc($keys, $params);
   }
 
-  function ensureKeys(array $defaults, ?array $params=null): void {
-    $this->access->ensureKeys($defaults, $params);
+  function ensureKeys(array $defaults, ?array $missings, ?array $params=null): void {
+    $this->access->ensureKeys($defaults, $missings, $params);
+  }
+
+  function deleteMissings(array $missings, ?array $params=null): void {
+    $this->access->deleteMissings($missings, $params);
   }
 
   function ensureOrder(array $keys, ?array $params=null): void {
diff --git a/src/schema/types/IType.php b/src/schema/types/IType.php
index e94fb80..c5fd8e3 100644
--- a/src/schema/types/IType.php
+++ b/src/schema/types/IType.php
@@ -47,30 +47,26 @@ interface IType {
    */
   function getPhpType(bool $allowNullable=true): ?string;
 
+  /**
+   * obtenir la valeur "inexistante" pour les objets de ce type
+   *
+   * si $valid reçoit la valeur false, il faut ignorer la valeur de retour:
+   * cela veut dire qu'il n'y a pas de valeur "inexistant" pour les valeurs de
+   * ce type
+   */
+  function getMissingValue(?bool &$valid=null);
+
   /** obtenir la valeur "nulle" pour les objets de ce type */
   function getNullValue();
 
   /**
-   * indiquer si c'est le type d'une valeur qui ne peut prendre que 2 états: une
-   * "vraie" et une "fausse"
+   * si c'est le type d'une valeur qui ne prendre qu'une liste prédéterminée
+   * d'états spécifiques, retourner le nombre d'états possibles, et mettre à
+   * jour $states avec les valeurs possibles
+   *
+   * sinon, retourner 0 et ne pas mettre $states à jour
    */
-  function is2States(): bool;
-
-  /**
-   * Si {@link is2States()} est vrai, retourner les deux valeurs [faux, vrai]
-   */
-  function get2States(): array;
-
-  /**
-   * indiquer si c'est le type d'une valeur qui ne peut prendre que 3 états: une
-   * "vraie", une "fausse", et une "indéterminée"
-   */
-  function is3States(): bool;
-
-  /**
-   * Si {@link is3States()} est vrai, retourner les 3 valeurs [faux, vrai, undef]
-   */
-  function get3States(): array;
+  function getNbStates(?array &$states=null): int;
 
   /** la donnée $input($valueKey) est-elle disponible? */
   function isAvailable(Input $input, $valueKey): bool;
diff --git a/src/schema/types/_tsimple.php b/src/schema/types/_tsimple.php
index 94ab013..fd8174a 100644
--- a/src/schema/types/_tsimple.php
+++ b/src/schema/types/_tsimple.php
@@ -43,20 +43,13 @@ abstract class _tsimple implements IType {
     return $phpType;
   }
 
-  function is2States(): bool {
+  function getMissingValue(?bool &$valid=null) {
+    $valid = true;
     return false;
   }
 
-  function get2States(): array {
-    throw StateException::not_implemented();
-  }
-
-  function is3States(): bool {
-    return false;
-  }
-
-  function get3States(): array {
-    throw StateException::not_implemented();
+  function getNbStates(?array &$states=null): int {
+    return 0;
   }
 
   function isAvailable(Input $input, $valueKey): bool {
diff --git a/src/schema/types/tbool.php b/src/schema/types/tbool.php
index 1d62eef..a9b7854 100644
--- a/src/schema/types/tbool.php
+++ b/src/schema/types/tbool.php
@@ -60,26 +60,25 @@ class tbool extends _tformatable {
     return "bool";
   }
 
-  function is2States(): bool {
-    return !$this->nullable;
-  }
-
-  function get2States(): array {
-    return [false, true];
-  }
-
-  function is3States(): bool {
-    return $this->nullable;
-  }
-
-  function get3States(): array {
-    return [false, true, null];
+  function getMissingValue(?bool &$valid=null) {
+    $valid = !$this->nullable;
+    return null;
   }
 
   function getNullValue() {
     return $this->nullable? null: false;
   }
 
+  public function getNbStates(?array &$states=null): int {
+    if ($this->nullable) {
+      $states = [false, true, null];
+      return 3;
+    } else {
+      $states = [false, true];
+      return 2;
+    }
+  }
+
   function isAvailable(Input $input, $valueKey): bool {
     return $input->isAvailable($valueKey);
   }
diff --git a/src/schema/types/tgeneric.php b/src/schema/types/tgeneric.php
index 9d948a6..498a16b 100644
--- a/src/schema/types/tgeneric.php
+++ b/src/schema/types/tgeneric.php
@@ -24,10 +24,6 @@ class tgeneric extends _tsimple {
     return null;
   }
 
-  function isAvailable(Input $input, $valueKey): bool {
-    return $input->isAvailable($valueKey);
-  }
-
   public function isNull($value): bool {
     return $value === null;
   }
diff --git a/src/schema/types/tmixed.php b/src/schema/types/tmixed.php
index 045cebf..3d64620 100644
--- a/src/schema/types/tmixed.php
+++ b/src/schema/types/tmixed.php
@@ -14,6 +14,11 @@ class tmixed extends _tsimple {
     return "mixed";
   }
 
+  function getMissingValue(?bool &$valid=null) {
+    $valid = false;
+    return null;
+  }
+
   function getNullValue() {
     return null;
   }
diff --git a/tests/php/access/KeyAccessTest.php b/tests/php/access/KeyAccessTest.php
index b654050..6c17fef 100644
--- a/tests/php/access/KeyAccessTest.php
+++ b/tests/php/access/KeyAccessTest.php
@@ -152,7 +152,7 @@ class KeyAccessTest extends TestCase {
 
   private function _ensureKeys(?array $orig, ?array $expected, array $defaults, ?array $params=null) {
     $v = $orig; $a = new KeyAccess($v);
-    $a->ensureKeys($defaults, $params);
+    $a->ensureKeys($defaults, $missings, $params);
     self::assertSame($expected, $v);
   }
   function testEnsureKeys() {
@@ -187,7 +187,7 @@ class KeyAccessTest extends TestCase {
     $v = $orig; $a = new KeyAccess($v);
     $keys = array_keys($defaults);
     $a->ensureAssoc($keys, $params);
-    $a->ensureKeys($defaults, $params);
+    $a->ensureKeys($defaults, $missings, $params);
     $a->ensureOrder($keys, $params);
     self::assertSame($expected, $v);
   }
diff --git a/tests/schema/_assoc/AssocSchemaTest.php b/tests/schema/_assoc/AssocSchemaTest.php
index c8e6c0d..d3314e1 100644
--- a/tests/schema/_assoc/AssocSchemaTest.php
+++ b/tests/schema/_assoc/AssocSchemaTest.php
@@ -50,54 +50,54 @@ class AssocSchemaTest extends TestCase {
     self::assertSame(self::schema([
       "type" => ["array"], "nullable" => true,
     ], [
-      "a" => [
+      "s" => [
         "type" => ["string"], "nullable" => false,
-        "name" => "a", "pkey" => "a", "header" => "a",
+        "name" => "s", "pkey" => "s", "header" => "s",
       ],
-    ]), AssocSchema::normalize_definition(["a" => "string"]));
+    ]), AssocSchema::normalize_definition(["s" => "string"]));
 
     self::assertSame(self::schema([
       "type" => ["array"], "nullable" => true,
     ], [
-      "a" => [
+      "s" => [
         "type" => ["string"], "nullable" => false,
-        "name" => "a", "pkey" => "a", "header" => "a",
+        "name" => "s", "pkey" => "s", "header" => "s",
+      ],
+      "i" => [
+        "type" => ["int"], "nullable" => false,
+        "name" => "i", "pkey" => "i", "header" => "i",
       ],
       "b" => [
-        "type" => ["int"], "nullable" => false,
+        "type" => ["bool"], "nullable" => false,
         "name" => "b", "pkey" => "b", "header" => "b",
       ],
-      "c" => [
-        "type" => ["bool"], "nullable" => false,
-        "name" => "c", "pkey" => "c", "header" => "c",
-      ],
     ]), AssocSchema::normalize_definition([
-      "a" => "string",
-      "b" => "int",
-      "c" => "bool",
+      "s" => "string",
+      "i" => "int",
+      "b" => "bool",
     ]));
   }
 
   function testConstructor() {
     $schema = new AssocSchema([
-      "a" => "string",
-      "b" => "int",
-      "c" => "bool",
+      "s" => "string",
+      "i" => "int",
+      "b" => "bool",
     ]);
     self::assertSame(self::schema([
       "type" => ["array"], "nullable" => true,
     ], [
-      "a" => [
+      "s" => [
         "type" => ["string"], "nullable" => false,
-        "name" => "a", "pkey" => "a", "header" => "a",
+        "name" => "s", "pkey" => "s", "header" => "s",
+      ],
+      "i" => [
+        "type" => ["int"], "nullable" => false,
+        "name" => "i", "pkey" => "i", "header" => "i",
       ],
       "b" => [
-        "type" => ["int"], "nullable" => false,
-        "name" => "b", "pkey" => "b", "header" => "b",
-      ],
-      "c" => [
         "type" => ["bool"], "nullable" => false,
-        "name" => "c", "pkey" => "c", "header" => "c",
+        "name" => "b", "pkey" => "b", "header" => "b",
       ],
     ]), $schema->getDefinition());
     //yaml::dump($schema->getDefinition());
@@ -105,69 +105,82 @@ class AssocSchemaTest extends TestCase {
 
   function testWrapper() {
     $schema = new AssocSchema([
-      "a" => "?string",
-      "b" => "?int",
-      "c" => "?bool",
+      "s" => "?string",
+      "i" => "?int",
+      "b" => "?bool",
     ]);
-    $array = ["a" => "  string  ", "b" => "  42 ", "c" => false];
+    $array = ["s" => "  string  ", "i" => "  42 ", "b" => false];
     $schema->getWrapper($array);
     self::assertSame([
-      "a" => "string",
-      "b" => 42,
-      "c" => false,
+      "s" => "string",
+      "i" => 42,
+      "b" => false,
     ], $array);
 
     ###########################################################################
     $schema = new AssocSchema([
-      "a" => "string",
-      "b" => "int",
-      "c" => "bool",
+      "s" => "string",
+      "i" => "int",
+      "b" => "bool",
     ]);
 
-    $array = ["a" => "  string  "];
+    $array = ["s" => "  string  "];
     $schema->getWrapper($array);
     self::assertSame([
-      "a" => "string",
-      "b" => 0,
-      "c" => false,
+      "s" => "string",
+      "i" => 0,
+      "b" => false,
     ], $array);
 
-    $array = ["c" => false, "a" => "  string  "];
+    $array = ["b" => false, "s" => "  string  "];
     $schema->getWrapper($array);
     self::assertSame([
-      "a" => "string",
-      "b" => 0,
-      "c" => false,
+      "s" => "string",
+      "i" => 0,
+      "b" => false,
     ], $array);
 
-    $array = ["a" => "  string  "];
+    $array = ["s" => "  string  "];
     $schema->getWrapper($array, null, ["ensure_order" => false]);
     self::assertSame([
-      "a" => "string",
-      "b" => 0,
-      "c" => false,
+      "s" => "string",
+      "i" => 0,
+      "b" => false,
     ], $array);
 
-    $array = ["c" => false, "a" => "  string  "];
+    $array = ["b" => false, "s" => "  string  "];
     $schema->getWrapper($array, null, ["ensure_order" => false]);
     self::assertSame([
-      "c" => false,
-      "a" => "string",
-      "b" => 0,
+      "b" => false,
+      "s" => "string",
+      "i" => 0,
     ], $array);
 
-    $array = ["a" => "  string  "];
+    $array = ["s" => "  string  "];
     $schema->getWrapper($array, null, ["ensure_keys" => false]);
     self::assertSame([
-      "a" => "string",
+      "s" => "string",
     ], $array);
 
-    $array = ["c" => false, "a" => "  string  "];
+    $array = ["b" => false, "s" => "  string  "];
     $schema->getWrapper($array, null, ["ensure_keys" => false]);
     self::assertSame([
-      "a" => "string",
-      "c" => false,
+      "s" => "string",
+      "b" => false,
     ], $array);
+
+    // false équivaut à absent
+    $array = ["s" => false, "i" => false, "b" => null];
+    $schema->getWrapper($array, null, ["ensure_keys" => true]);
+    self::assertSame([
+      "s" => "",
+      "i" => 0,
+      "b" => false,
+    ], $array);
+
+    $array = ["s" => false, "i" => false, "b" => null];
+    $schema->getWrapper($array, null, ["ensure_keys" => false]);
+    self::assertSame([], $array);
   }
 
   const STRING_SCHEMA = [
@@ -203,7 +216,7 @@ class AssocSchemaTest extends TestCase {
 
     $array = self::STRINGS;
     $wrapper = $schema->getWrapper($array, null, ["throw" => false]);
-    self::assertSame(["s" => "string", "f" => false, "m" => ""], $array);
+    self::assertSame(["s" => "string", "f" => "", "m" => ""], $array);
     $result = $wrapper->getResult("s");
     self::assertTrue($result->normalized);
     $result = $wrapper->getResult("f");
@@ -241,7 +254,7 @@ class AssocSchemaTest extends TestCase {
 
     $array = self::STRINGS;
     $wrapper = $schema->getWrapper($array, null, ["throw" => false]);
-    self::assertSame(["s" => "string", "f" => false, "m" => null], $array);
+    self::assertSame(["s" => "string", "f" => null, "m" => null], $array);
     $result = $wrapper->getResult("s");
     self::assertTrue($result->normalized);
     $result = $wrapper->getResult("f");
@@ -277,7 +290,7 @@ class AssocSchemaTest extends TestCase {
 
     $array = self::STRINGS;
     $wrapper = $schema->getWrapper($array, null, ["throw" => false]);
-    self::assertSame(["s" => "string", "f" => false, "m" => ""], $array);
+    self::assertSame(["s" => "string", "f" => "", "m" => ""], $array);
     $result = $wrapper->getResult("s");
     self::assertTrue($result->normalized);
     $result = $wrapper->getResult("f");
@@ -318,7 +331,7 @@ class AssocSchemaTest extends TestCase {
 
     $array = self::STRINGS;
     $wrapper = $schema->getWrapper($array, null, ["throw" => false]);
-    self::assertSame(["s" => "string", "f" => false, "m" => null], $array);
+    self::assertSame(["s" => "string", "f" => null, "m" => null], $array);
     $result = $wrapper->getResult("s");
     self::assertTrue($result->normalized);
     $result = $wrapper->getResult("f");