diff --git a/CHANGELOG.md b/CHANGELOG.md
index ec31d45..7117179 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,19 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## 0.16.1 — 2026-10-17
+
+- **Fixed.** A closed object (`additionalProperties: false`) whose declared
+  member fails its own subschema no longer receives an extra
+  `additionalProperties` violation of the parent over the member's own
+  failure (#175). The backend marks a member as evaluated only when every
+  declared member passed, so the failing one still counted as unchecked when
+  `additionalProperties` ran; a member the sibling `properties` map declares,
+  or one of its `patternProperties` patterns matches, is now what the leaf
+  filter treats as not additional. An undeclared member, and a member that
+  fails the object form of `additionalProperties`, keep their leaves; the
+  verdict never moved.
+
 ## 0.16.0 — 2026-10-11
 
 - **Added.** OpenAPI 3.1 schemas now support `prefixItems`, `contains` with
diff --git a/src/Internal/Schema/SchemaValidator.php b/src/Internal/Schema/SchemaValidator.php
index 22a1523..352cfa5 100644
--- a/src/Internal/Schema/SchemaValidator.php
+++ b/src/Internal/Schema/SchemaValidator.php
@@ -5,6 +5,7 @@
 namespace Rasuvaeff\OpenApiContract\Internal\Schema;
 
 use Opis\JsonSchema\Errors\ValidationError;
+use Opis\JsonSchema\Helper;
 use Opis\JsonSchema\Schema;
 use Opis\JsonSchema\SchemaLoader;
 use Opis\JsonSchema\Schemas\ExceptionSchema;
@@ -233,6 +234,9 @@ private function leaf(ValidationError $error): array
     {
         $path = $this->dataPath($error);
         $expected = $this->assertion($error);
+        if ($this->isSpuriousAdditionalProperties($error)) {
+            return [];
+        }
         if ($error->keyword() === 'required') {
             /** @var mixed $missing */
             $missing = $error->args()['missing'] ?? null;
@@ -251,6 +255,69 @@ private function leaf(ValidationError $error): array
         return [new SchemaFailure(path: $path, keyword: $error->keyword(), actual: $error->data()->value(), expected: $expected)];
     }
 
+    /**
+     * A closed object (`additionalProperties: false`) whose declared member
+     * fails its own subschema still receives an `additionalProperties` error
+     * naming it: the backend marks a member as evaluated only when every
+     * declared member passed, so the failing one counts as unchecked by the
+     * time `additionalProperties` runs. A member the sibling `properties`
+     * map declares, or one of its `patternProperties` patterns matches, is
+     * not additional — its own subschema is what the `properties` keyword
+     * judged, and its failure is already reported there. If no flagged name
+     * escapes that, the leaf exists only because of the missing mark and is
+     * dropped.
+     *
+     * The object form of `additionalProperties` is left alone: there the
+     * backend itself judges the flagged members against the added schema,
+     * so a name it reports there failed both the declaration and it.
+     */
+    private function isSpuriousAdditionalProperties(ValidationError $error): bool
+    {
+        if ($error->keyword() !== 'additionalProperties') {
+            return false;
+        }
+        /** @var mixed $flagged */
+        $flagged = $error->args()['properties'] ?? null;
+        if (!is_array($flagged)) {
+            return false;
+        }
+        $schema = $error->schema()->info()->data();
+        if (!$schema instanceof \stdClass || !property_exists($schema, 'additionalProperties') || $schema->additionalProperties !== false) {
+            return false;
+        }
+
+        /** @var mixed $declared */
+        $declared = $schema->properties ?? null;
+        /** @var mixed $patterned */
+        $patterned = $schema->patternProperties ?? null;
+        /** @var array<array-key, mixed> $patterns */
+        $patterns = is_array($patterned) ? $patterned : (is_object($patterned) ? (array) $patterned : []);
+
+        foreach ($flagged as $name) {
+            if (!is_string($name)) {
+                return false;
+            }
+            if (is_object($declared) && property_exists($declared, $name)) {
+                continue;
+            }
+            foreach (array_keys($patterns) as $pattern) {
+                if (!is_string($pattern) || $pattern === '') {
+                    continue;
+                }
+                // The delimiter prefix and the flags make the pattern non-empty in every case psalm already narrowed `$pattern` to non-empty-string.
+                /** @var non-empty-string $regex */
+                $regex = Helper::patternToRegex($pattern);
+                if (preg_match($regex, $name) === 1) {
+                    continue 2;
+                }
+            }
+
+            return false;
+        }
+
+        return true;
+    }
+
     /**
      * The assertion an error is about: the keyword and its value in the
      * subschema that carries it, as the compiler spelled it.
diff --git a/tests/ContractTest.php b/tests/ContractTest.php
index a077b2b..8a55c14 100644
--- a/tests/ContractTest.php
+++ b/tests/ContractTest.php
@@ -570,16 +570,19 @@ public function validatesARecursiveSchemaAtEveryDepth(): void
 
         $valid = '{"name":"a","children":[{"name":"b","children":[{"name":"c","children":[{"name":"d"}]}]}]}';
         Assert::true($contract->validateRequest($request($valid))->isValid());
+        // The four older leaf rungs — the two genuine failures here, and the
+        // backend's spurious `additionalProperties` at each closed ancestor
+        // whose declared member carried the failure (#175) — are now two.
         Assert::same(
             array_map(static fn(Violation $v): string => $v->code, $contract->validateRequest($request('{"name":"a","children":[{"name":"b","children":[{"nam":"c"}]}]}'))->violations),
-            ['request.body.schema', 'request.body.schema', 'request.body.schema', 'request.body.schema'],
+            ['request.body.schema', 'request.body.schema'],
         );
         // `id` is readOnly: never demanded on a request, at any depth, and
         // demanded at every depth of a response.
         Assert::true($contract->validateRequest($request('{"name":"a","children":[{"name":"b","id":1}]}'))->isValid());
         Assert::same(
             array_map(static fn(Violation $v): string => $v->code, $contract->validateResponse('tree.create', $response($valid))->violations),
-            ['response.body.schema', 'response.body.schema', 'response.body.schema', 'response.body.schema', 'response.body.schema', 'response.body.schema', 'response.body.schema'],
+            ['response.body.schema', 'response.body.schema', 'response.body.schema', 'response.body.schema'],
         );
         Assert::true($contract->validateResponse('tree.create', $response('{"id":1,"name":"a","children":[{"id":2,"name":"b","children":[{"id":3,"name":"c"}]}]}'))->isValid());
 
@@ -685,7 +688,7 @@ public function validatesASharedComponentDeferredToDefs(): void
         Assert::true($contract->validateRequest($request(sprintf('{"sendTo":[%s],"billTo":[%s]}', $noCode, $address([]))))->isValid());
         Assert::same(
             array_map(static fn(Violation $v): string => $v->code, $contract->validateRequest($request(sprintf('{"sendTo":[%s],"billTo":[%s]}', $address([]), $address(['city' => 5]))))->violations),
-            ['request.body.schema', 'request.body.schema'],
+            ['request.body.schema'],
         );
         Assert::true($contract->validateResponse('parcels.create', $response(sprintf('{"sendTo":[%s],"billTo":[%s],"code":1}', $address([]), $address([]))))->isValid());
         Assert::same(
diff --git a/tests/SchemaValidatorTest.php b/tests/SchemaValidatorTest.php
index 6bae685..bd79cfa 100644
--- a/tests/SchemaValidatorTest.php
+++ b/tests/SchemaValidatorTest.php
@@ -1063,6 +1063,80 @@ public function reportsLeafFailuresWithTheirPathAndKeyword(): void
         Assert::same($deep[19]->path, ['p9', 'r']);
     }
 
+    /**
+     * A closed object's declared member failing its own subschema is not
+     * additionally reported as an `additionalProperties` failure of the
+     * parent (#175): the backend marks a member as evaluated only when every
+     * declared member passed, so the failing one is still unchecked when
+     * `additionalProperties: false` runs. An undeclared member is a real
+     * failure of it and keeps its leaf; so does a member that failed the
+     * object form of `additionalProperties`, which the backend carries on
+     * the member's own path.
+     */
+    public function closedObjectDoesNotReportItsDeclaredMemberAsAdditional(): void
+    {
+        $validator = new SchemaValidator();
+        $closed = [
+            'type' => 'object',
+            'additionalProperties' => false,
+            'required' => ['a'],
+            'properties' => ['a' => ['type' => 'array', 'minItems' => 1]],
+        ];
+
+        // The declared member fails its own subschema: its leaf, and no word
+        // about `additionalProperties` at the root.
+        Assert::false($validator->isValid(json_decode('{"a":[]}'), $closed, SchemaDialect::OpenApi31));
+        Assert::same(
+            $this->render($validator->failures(json_decode('{"a":[]}'), $closed, SchemaDialect::OpenApi31)),
+            [['a', 'minItems', []]],
+        );
+
+        // An undeclared member beside it is `additionalProperties`'s to report.
+        Assert::same(
+            $this->render($validator->failures(json_decode('{"a":[],"b":1}'), $closed, SchemaDialect::OpenApi31)),
+            [['a', 'minItems', []], ['', 'additionalProperties', ['a' => [], 'b' => 1]]],
+        );
+
+        // A name `patternProperties` matches is no more additional dropped.
+        $patternClosed = [
+            'type' => 'object',
+            'additionalProperties' => false,
+            'patternProperties' => ['^x-' => ['type' => 'integer']],
+            'properties' => ['x-a' => ['type' => 'integer']],
+        ];
+        Assert::same(
+            $this->render($validator->failures(json_decode('{"x-a":"3"}'), $patternClosed, SchemaDialect::OpenApi31)),
+            [['x-a', 'type', '3']],
+        );
+        Assert::same(
+            $this->render($validator->failures(json_decode('{"x-a":"3","count":9}'), $patternClosed, SchemaDialect::OpenApi31)),
+            [['x-a', 'type', '3'], ['', 'additionalProperties', ['x-a' => '3', 'count' => 9]]],
+        );
+
+        // Nested closed objects: the same at the member's own path.
+        $nested = ['type' => 'object', 'additionalProperties' => false, 'properties' => ['inner' => [
+            'type' => 'object',
+            'additionalProperties' => false,
+            'properties' => ['i' => ['type' => 'string', 'minLength' => 2]],
+        ]]];
+        Assert::same(
+            $this->render($validator->failures(json_decode('{"inner":{"i":"x"}}'), $nested, SchemaDialect::OpenApi31)),
+            [['inner.i', 'minLength', 'x']],
+        );
+        Assert::same(
+            $this->render($validator->failures(json_decode('{"inner":{"i":"x","j":2}}'), $nested, SchemaDialect::OpenApi31)),
+            [['inner.i', 'minLength', 'x'], ['inner', 'additionalProperties', ['i' => 'x', 'j' => 2]]],
+        );
+
+        // The object form is untouched: a member failing it as well is named
+        // on its own path, under each keyword.
+        $open = ['type' => 'object', 'properties' => ['s' => ['type' => 'integer']], 'additionalProperties' => ['minLength' => 5]];
+        Assert::same(
+            $this->render($validator->failures(json_decode('{"s":"x"}'), $open, SchemaDialect::OpenApi31)),
+            [['s', 'type', 'x'], ['s', 'minLength', 'x']],
+        );
+    }
+
     /**
      * A discriminated union's diagnostics follow the branch the value names
      * — through `mapping` as a reference or a component name, or implicitly