async-aws · Amoifr · Sep 3, 2026
diff --git a/psalm.baseline.xml b/psalm.baseline.xml
@@ -52,14 +52,4 @@
       <code><![CDATA[$s3SignerOptions]]></code>
     </NoValue>
   </file>
-  <file src="src/Service/StepFunctions/src/Result/StartExecutionOutput.php">
-    <PossiblyFalsePropertyAssignmentValue>
-      <code><![CDATA[$d = \DateTimeImmutable::createFromFormat('U.u', \sprintf('%.6F', $data['startDate']))]]></code>
-    </PossiblyFalsePropertyAssignmentValue>
-  </file>
-  <file src="src/Service/StepFunctions/src/Result/StopExecutionOutput.php">
-    <PossiblyFalsePropertyAssignmentValue>
-      <code><![CDATA[$d = \DateTimeImmutable::createFromFormat('U.u', \sprintf('%.6F', $data['stopDate']))]]></code>
-    </PossiblyFalsePropertyAssignmentValue>
-  </file>
 </files>
diff --git a/src/CodeGenerator/src/Generator/ResponseParser/JsonRpcParser.php b/src/CodeGenerator/src/Generator/ResponseParser/JsonRpcParser.php
@@ -16,7 +16,7 @@ class JsonRpcParser extends RestJsonParser
     protected function parseResponseTimestamp(Shape $shape, string $input, bool $required): string
     {
         if ($required) {
-            $body = '/** @var \DateTimeImmutable $d */ $d = \DateTimeImmutable::createFromFormat(\'U.u\', \sprintf(\'%.6F\', INPUT))';
+            $body = $this->rejectUnparsableTimestamp('\DateTimeImmutable::createFromFormat(\'U.u\', \sprintf(\'%.6F\', INPUT))');
         } else {
             $body = '(isset(INPUT) && ($d = \DateTimeImmutable::createFromFormat(\'U.u\', \sprintf(\'%.6F\', INPUT)))) ? $d : null';
         }

diff --git a/src/CodeGenerator/src/Generator/ResponseParser/RestJsonParser.php b/src/CodeGenerator/src/Generator/ResponseParser/RestJsonParser.php
@@ -19,6 +19,7 @@
 use AsyncAws\CodeGenerator\Generator\GeneratorHelper;
 use AsyncAws\CodeGenerator\Generator\Naming\ClassName;
 use AsyncAws\CodeGenerator\Generator\Naming\NamespaceRegistry;
+use AsyncAws\Core\Exception\UnparsableResponse;
 use Nette\PhpGenerator\Method;
 use Nette\PhpGenerator\Visibility;
 
@@ -161,14 +162,28 @@ protected function parseResponseTimestamp(Shape $shape, string $input, bool $req
         }
 
         if ($required) {
-            $body = '/** @var \DateTimeImmutable $d */ $d = ' . $body;
+            $body = $this->rejectUnparsableTimestamp($body);
         } else {
             $body = 'isset(INPUT) && ($d = ' . $body . ') ? $d : null';
         }
 
         return strtr($body, ['INPUT' => $input]);
     }
 
+    /**
+     * createFromFormat() returns false on a malformed value, and no annotation convinces static
+     * analysis that it cannot happen here. The failure is raised instead, so that the generated
+     * code needs no baseline entry: the value comes from the response, which is exactly what
+     * UnparsableResponse describes.
+     */
+    protected function rejectUnparsableTimestamp(string $body): string
+    {
+        $className = ClassName::createFromFqdn(UnparsableResponse::class);
+        $this->imports[] = $className;
+
+        return $body . ' ?: throw new ' . $className->getName() . "('Invalid timestamp received.')";
+    }
+
     private function getInputAccessorName(Member $member): string
     {
         if ($member instanceof StructureMember) {

diff --git a/src/Service/DynamoDb/CHANGELOG.md b/src/Service/DynamoDb/CHANGELOG.md
@@ -6,6 +6,10 @@
 
 - AWS api-change: Vector indexes are a type of index in Amazon DynamoDB that enable similarity search on vector embedding stored in your table items. Vector indexes use approximate nearest neighbor search to find items whose vectors are most similar to a query vector that you provide.
 
+### Changed
+
+- Throw `UnparsableResponse` instead of a `TypeError` when a required timestamp cannot be parsed
+
 ## 3.11.0
 
 ### Added

diff --git a/src/Service/DynamoDb/src/Result/CreateTableOutput.php b/src/Service/DynamoDb/src/Result/CreateTableOutput.php
@@ -2,6 +2,7 @@
 
 namespace AsyncAws\DynamoDb\Result;
 
+use AsyncAws\Core\Exception\UnparsableResponse;
 use AsyncAws\Core\Response;
 use AsyncAws\Core\Result;
 use AsyncAws\DynamoDb\Enum\BillingMode;
@@ -332,7 +333,7 @@ private function populateResultRestoreSummary(array $json): RestoreSummary
         return new RestoreSummary([
             'SourceBackupArn' => isset($json['SourceBackupArn']) ? (string) $json['SourceBackupArn'] : null,
             'SourceTableArn' => isset($json['SourceTableArn']) ? (string) $json['SourceTableArn'] : null,
-            'RestoreDateTime' => /** @var \DateTimeImmutable $d */ $d = \DateTimeImmutable::createFromFormat('U.u', \sprintf('%.6F', $json['RestoreDateTime'])),
+            'RestoreDateTime' => \DateTimeImmutable::createFromFormat('U.u', \sprintf('%.6F', $json['RestoreDateTime'])) ?: throw new UnparsableResponse('Invalid timestamp received.'),
             'RestoreInProgress' => filter_var($json['RestoreInProgress'], \FILTER_VALIDATE_BOOLEAN),
         ]);
     }

diff --git a/src/Service/DynamoDb/src/Result/DeleteTableOutput.php b/src/Service/DynamoDb/src/Result/DeleteTableOutput.php
@@ -2,6 +2,7 @@
 
 namespace AsyncAws\DynamoDb\Result;
 
+use AsyncAws\Core\Exception\UnparsableResponse;
 use AsyncAws\Core\Response;
 use AsyncAws\Core\Result;
 use AsyncAws\DynamoDb\Enum\BillingMode;
@@ -332,7 +333,7 @@ private function populateResultRestoreSummary(array $json): RestoreSummary
         return new RestoreSummary([
             'SourceBackupArn' => isset($json['SourceBackupArn']) ? (string) $json['SourceBackupArn'] : null,
             'SourceTableArn' => isset($json['SourceTableArn']) ? (string) $json['SourceTableArn'] : null,
-            'RestoreDateTime' => /** @var \DateTimeImmutable $d */ $d = \DateTimeImmutable::createFromFormat('U.u', \sprintf('%.6F', $json['RestoreDateTime'])),
+            'RestoreDateTime' => \DateTimeImmutable::createFromFormat('U.u', \sprintf('%.6F', $json['RestoreDateTime'])) ?: throw new UnparsableResponse('Invalid timestamp received.'),
             'RestoreInProgress' => filter_var($json['RestoreInProgress'], \FILTER_VALIDATE_BOOLEAN),
         ]);
     }

diff --git a/src/Service/DynamoDb/src/Result/DescribeTableOutput.php b/src/Service/DynamoDb/src/Result/DescribeTableOutput.php
@@ -2,6 +2,7 @@
 
 namespace AsyncAws\DynamoDb\Result;
 
+use AsyncAws\Core\Exception\UnparsableResponse;
 use AsyncAws\Core\Response;
 use AsyncAws\Core\Result;
 use AsyncAws\DynamoDb\Enum\BillingMode;
@@ -332,7 +333,7 @@ private function populateResultRestoreSummary(array $json): RestoreSummary
         return new RestoreSummary([
             'SourceBackupArn' => isset($json['SourceBackupArn']) ? (string) $json['SourceBackupArn'] : null,
             'SourceTableArn' => isset($json['SourceTableArn']) ? (string) $json['SourceTableArn'] : null,
-            'RestoreDateTime' => /** @var \DateTimeImmutable $d */ $d = \DateTimeImmutable::createFromFormat('U.u', \sprintf('%.6F', $json['RestoreDateTime'])),
+            'RestoreDateTime' => \DateTimeImmutable::createFromFormat('U.u', \sprintf('%.6F', $json['RestoreDateTime'])) ?: throw new UnparsableResponse('Invalid timestamp received.'),
             'RestoreInProgress' => filter_var($json['RestoreInProgress'], \FILTER_VALIDATE_BOOLEAN),
         ]);
     }

diff --git a/src/Service/DynamoDb/src/Result/UpdateTableOutput.php b/src/Service/DynamoDb/src/Result/UpdateTableOutput.php
@@ -2,6 +2,7 @@
 
 namespace AsyncAws\DynamoDb\Result;
 
+use AsyncAws\Core\Exception\UnparsableResponse;
 use AsyncAws\Core\Response;
 use AsyncAws\Core\Result;
 use AsyncAws\DynamoDb\Enum\BillingMode;
@@ -332,7 +333,7 @@ private function populateResultRestoreSummary(array $json): RestoreSummary
         return new RestoreSummary([
             'SourceBackupArn' => isset($json['SourceBackupArn']) ? (string) $json['SourceBackupArn'] : null,
             'SourceTableArn' => isset($json['SourceTableArn']) ? (string) $json['SourceTableArn'] : null,
-            'RestoreDateTime' => /** @var \DateTimeImmutable $d */ $d = \DateTimeImmutable::createFromFormat('U.u', \sprintf('%.6F', $json['RestoreDateTime'])),
+            'RestoreDateTime' => \DateTimeImmutable::createFromFormat('U.u', \sprintf('%.6F', $json['RestoreDateTime'])) ?: throw new UnparsableResponse('Invalid timestamp received.'),
             'RestoreInProgress' => filter_var($json['RestoreInProgress'], \FILTER_VALIDATE_BOOLEAN),
         ]);
     }

diff --git a/src/Service/Kinesis/CHANGELOG.md b/src/Service/Kinesis/CHANGELOG.md
@@ -9,6 +9,7 @@
 
 ### Changed
 
+- Throw `UnparsableResponse` instead of a `TypeError` when a required timestamp cannot be parsed
 - AWS enhancement: Documentation updates.
 
 ## 3.5.0

diff --git a/src/Service/Kinesis/src/Result/DescribeStreamConsumerOutput.php b/src/Service/Kinesis/src/Result/DescribeStreamConsumerOutput.php
@@ -2,6 +2,7 @@
 
 namespace AsyncAws\Kinesis\Result;
 
+use AsyncAws\Core\Exception\UnparsableResponse;
 use AsyncAws\Core\Response;
 use AsyncAws\Core\Result;
 use AsyncAws\Kinesis\Enum\ConsumerStatus;
@@ -36,7 +37,7 @@ private function populateResultConsumerDescription(array $json): ConsumerDescrip
             'ConsumerName' => (string) $json['ConsumerName'],
             'ConsumerARN' => (string) $json['ConsumerARN'],
             'ConsumerStatus' => !ConsumerStatus::exists((string) $json['ConsumerStatus']) ? ConsumerStatus::UNKNOWN_TO_SDK : (string) $json['ConsumerStatus'],
-            'ConsumerCreationTimestamp' => /** @var \DateTimeImmutable $d */ $d = \DateTimeImmutable::createFromFormat('U.u', \sprintf('%.6F', $json['ConsumerCreationTimestamp'])),
+            'ConsumerCreationTimestamp' => \DateTimeImmutable::createFromFormat('U.u', \sprintf('%.6F', $json['ConsumerCreationTimestamp'])) ?: throw new UnparsableResponse('Invalid timestamp received.'),
             'StreamARN' => (string) $json['StreamARN'],
         ]);
     }

diff --git a/src/Service/Kinesis/src/Result/DescribeStreamOutput.php b/src/Service/Kinesis/src/Result/DescribeStreamOutput.php
@@ -3,6 +3,7 @@
 namespace AsyncAws\Kinesis\Result;
 
 use AsyncAws\Core\Exception\InvalidArgument;
+use AsyncAws\Core\Exception\UnparsableResponse;
 use AsyncAws\Core\Response;
 use AsyncAws\Core\Result;
 use AsyncAws\Kinesis\Enum\EncryptionType;
@@ -174,7 +175,7 @@ private function populateResultStreamDescription(array $json): StreamDescription
             'Shards' => $this->populateResultShardList($json['Shards']),
             'HasMoreShards' => filter_var($json['HasMoreShards'], \FILTER_VALIDATE_BOOLEAN),
             'RetentionPeriodHours' => (int) $json['RetentionPeriodHours'],
-            'StreamCreationTimestamp' => /** @var \DateTimeImmutable $d */ $d = \DateTimeImmutable::createFromFormat('U.u', \sprintf('%.6F', $json['StreamCreationTimestamp'])),
+            'StreamCreationTimestamp' => \DateTimeImmutable::createFromFormat('U.u', \sprintf('%.6F', $json['StreamCreationTimestamp'])) ?: throw new UnparsableResponse('Invalid timestamp received.'),
             'EnhancedMonitoring' => $this->populateResultEnhancedMonitoringList($json['EnhancedMonitoring']),
             'EncryptionType' => isset($json['EncryptionType']) ? (!EncryptionType::exists((string) $json['EncryptionType']) ? EncryptionType::UNKNOWN_TO_SDK : (string) $json['EncryptionType']) : null,
             'KeyId' => isset($json['KeyId']) ? (string) $json['KeyId'] : null,

diff --git a/src/Service/Kinesis/src/Result/DescribeStreamSummaryOutput.php b/src/Service/Kinesis/src/Result/DescribeStreamSummaryOutput.php
@@ -2,6 +2,7 @@
 
 namespace AsyncAws\Kinesis\Result;
 
+use AsyncAws\Core\Exception\UnparsableResponse;
 use AsyncAws\Core\Response;
 use AsyncAws\Core\Result;
 use AsyncAws\Kinesis\Enum\EncryptionType;
@@ -84,7 +85,7 @@ private function populateResultStreamDescriptionSummary(array $json): StreamDesc
             'StreamStatus' => !StreamStatus::exists((string) $json['StreamStatus']) ? StreamStatus::UNKNOWN_TO_SDK : (string) $json['StreamStatus'],
             'StreamModeDetails' => empty($json['StreamModeDetails']) ? null : $this->populateResultStreamModeDetails($json['StreamModeDetails']),
             'RetentionPeriodHours' => (int) $json['RetentionPeriodHours'],
-            'StreamCreationTimestamp' => /** @var \DateTimeImmutable $d */ $d = \DateTimeImmutable::createFromFormat('U.u', \sprintf('%.6F', $json['StreamCreationTimestamp'])),
+            'StreamCreationTimestamp' => \DateTimeImmutable::createFromFormat('U.u', \sprintf('%.6F', $json['StreamCreationTimestamp'])) ?: throw new UnparsableResponse('Invalid timestamp received.'),
             'EnhancedMonitoring' => $this->populateResultEnhancedMonitoringList($json['EnhancedMonitoring']),
             'EncryptionType' => isset($json['EncryptionType']) ? (!EncryptionType::exists((string) $json['EncryptionType']) ? EncryptionType::UNKNOWN_TO_SDK : (string) $json['EncryptionType']) : null,
             'KeyId' => isset($json['KeyId']) ? (string) $json['KeyId'] : null,

diff --git a/src/Service/Kinesis/src/Result/ListStreamConsumersOutput.php b/src/Service/Kinesis/src/Result/ListStreamConsumersOutput.php
@@ -3,6 +3,7 @@
 namespace AsyncAws\Kinesis\Result;
 
 use AsyncAws\Core\Exception\InvalidArgument;
+use AsyncAws\Core\Exception\UnparsableResponse;
 use AsyncAws\Core\Response;
 use AsyncAws\Core\Result;
 use AsyncAws\Kinesis\Enum\ConsumerStatus;
@@ -113,7 +114,7 @@ private function populateResultConsumer(array $json): Consumer
             'ConsumerName' => (string) $json['ConsumerName'],
             'ConsumerARN' => (string) $json['ConsumerARN'],
             'ConsumerStatus' => !ConsumerStatus::exists((string) $json['ConsumerStatus']) ? ConsumerStatus::UNKNOWN_TO_SDK : (string) $json['ConsumerStatus'],
-            'ConsumerCreationTimestamp' => /** @var \DateTimeImmutable $d */ $d = \DateTimeImmutable::createFromFormat('U.u', \sprintf('%.6F', $json['ConsumerCreationTimestamp'])),
+            'ConsumerCreationTimestamp' => \DateTimeImmutable::createFromFormat('U.u', \sprintf('%.6F', $json['ConsumerCreationTimestamp'])) ?: throw new UnparsableResponse('Invalid timestamp received.'),
         ]);
     }
 

diff --git a/src/Service/Kinesis/src/Result/RegisterStreamConsumerOutput.php b/src/Service/Kinesis/src/Result/RegisterStreamConsumerOutput.php
@@ -2,6 +2,7 @@
 
 namespace AsyncAws\Kinesis\Result;
 
+use AsyncAws\Core\Exception\UnparsableResponse;
 use AsyncAws\Core\Response;
 use AsyncAws\Core\Result;
 use AsyncAws\Kinesis\Enum\ConsumerStatus;
@@ -37,7 +38,7 @@ private function populateResultConsumer(array $json): Consumer
             'ConsumerName' => (string) $json['ConsumerName'],
             'ConsumerARN' => (string) $json['ConsumerARN'],
             'ConsumerStatus' => !ConsumerStatus::exists((string) $json['ConsumerStatus']) ? ConsumerStatus::UNKNOWN_TO_SDK : (string) $json['ConsumerStatus'],
-            'ConsumerCreationTimestamp' => /** @var \DateTimeImmutable $d */ $d = \DateTimeImmutable::createFromFormat('U.u', \sprintf('%.6F', $json['ConsumerCreationTimestamp'])),
+            'ConsumerCreationTimestamp' => \DateTimeImmutable::createFromFormat('U.u', \sprintf('%.6F', $json['ConsumerCreationTimestamp'])) ?: throw new UnparsableResponse('Invalid timestamp received.'),
         ]);
     }
 }
diff --git a/src/Service/S3Vectors/CHANGELOG.md b/src/Service/S3Vectors/CHANGELOG.md
@@ -2,6 +2,10 @@
 
 ## NOT RELEASED
 
+### Changed
+
+- Throw `UnparsableResponse` instead of a `TypeError` when a required timestamp cannot be parsed
+
 ## 2.1.0
 
 ### Added

diff --git a/src/Service/S3Vectors/src/Result/GetIndexOutput.php b/src/Service/S3Vectors/src/Result/GetIndexOutput.php
@@ -2,6 +2,7 @@
 
 namespace AsyncAws\S3Vectors\Result;
 
+use AsyncAws\Core\Exception\UnparsableResponse;
 use AsyncAws\Core\Response;
 use AsyncAws\Core\Result;
 use AsyncAws\S3Vectors\Enum\DataType;
@@ -48,7 +49,7 @@ private function populateResultIndex(array $json): Index
             'vectorBucketName' => (string) $json['vectorBucketName'],
             'indexName' => (string) $json['indexName'],
             'indexArn' => (string) $json['indexArn'],
-            'creationTime' => /** @var \DateTimeImmutable $d */ $d = \DateTimeImmutable::createFromFormat('U.u', \sprintf('%.6F', $json['creationTime'])),
+            'creationTime' => \DateTimeImmutable::createFromFormat('U.u', \sprintf('%.6F', $json['creationTime'])) ?: throw new UnparsableResponse('Invalid timestamp received.'),
             'dataType' => !DataType::exists((string) $json['dataType']) ? DataType::UNKNOWN_TO_SDK : (string) $json['dataType'],
             'dimension' => (int) $json['dimension'],
             'distanceMetric' => !DistanceMetric::exists((string) $json['distanceMetric']) ? DistanceMetric::UNKNOWN_TO_SDK : (string) $json['distanceMetric'],

diff --git a/src/Service/S3Vectors/src/Result/GetVectorBucketOutput.php b/src/Service/S3Vectors/src/Result/GetVectorBucketOutput.php
@@ -2,6 +2,7 @@
 
 namespace AsyncAws\S3Vectors\Result;
 
+use AsyncAws\Core\Exception\UnparsableResponse;
 use AsyncAws\Core\Response;
 use AsyncAws\Core\Result;
 use AsyncAws\S3Vectors\Enum\SseType;
@@ -44,7 +45,7 @@ private function populateResultVectorBucket(array $json): VectorBucket
         return new VectorBucket([
             'vectorBucketName' => (string) $json['vectorBucketName'],
             'vectorBucketArn' => (string) $json['vectorBucketArn'],
-            'creationTime' => /** @var \DateTimeImmutable $d */ $d = \DateTimeImmutable::createFromFormat('U.u', \sprintf('%.6F', $json['creationTime'])),
+            'creationTime' => \DateTimeImmutable::createFromFormat('U.u', \sprintf('%.6F', $json['creationTime'])) ?: throw new UnparsableResponse('Invalid timestamp received.'),
             'encryptionConfiguration' => empty($json['encryptionConfiguration']) ? null : $this->populateResultEncryptionConfiguration($json['encryptionConfiguration']),
         ]);
     }

diff --git a/src/Service/S3Vectors/src/Result/ListIndexesOutput.php b/src/Service/S3Vectors/src/Result/ListIndexesOutput.php
@@ -3,6 +3,7 @@
 namespace AsyncAws\S3Vectors\Result;
 
 use AsyncAws\Core\Exception\InvalidArgument;
+use AsyncAws\Core\Exception\UnparsableResponse;
 use AsyncAws\Core\Response;
 use AsyncAws\Core\Result;
 use AsyncAws\S3Vectors\Input\ListIndexesInput;
@@ -103,7 +104,7 @@ private function populateResultIndexSummary(array $json): IndexSummary
             'vectorBucketName' => (string) $json['vectorBucketName'],
             'indexName' => (string) $json['indexName'],
             'indexArn' => (string) $json['indexArn'],
-            'creationTime' => /** @var \DateTimeImmutable $d */ $d = \DateTimeImmutable::createFromFormat('U.u', \sprintf('%.6F', $json['creationTime'])),
+            'creationTime' => \DateTimeImmutable::createFromFormat('U.u', \sprintf('%.6F', $json['creationTime'])) ?: throw new UnparsableResponse('Invalid timestamp received.'),
         ]);
     }
 

diff --git a/src/Service/S3Vectors/src/Result/ListVectorBucketsOutput.php b/src/Service/S3Vectors/src/Result/ListVectorBucketsOutput.php
@@ -3,6 +3,7 @@
 namespace AsyncAws\S3Vectors\Result;
 
 use AsyncAws\Core\Exception\InvalidArgument;
+use AsyncAws\Core\Exception\UnparsableResponse;
 use AsyncAws\Core\Response;
 use AsyncAws\Core\Result;
 use AsyncAws\S3Vectors\Input\ListVectorBucketsInput;
@@ -115,7 +116,7 @@ private function populateResultVectorBucketSummary(array $json): VectorBucketSum
         return new VectorBucketSummary([
             'vectorBucketName' => (string) $json['vectorBucketName'],
             'vectorBucketArn' => (string) $json['vectorBucketArn'],
-            'creationTime' => /** @var \DateTimeImmutable $d */ $d = \DateTimeImmutable::createFromFormat('U.u', \sprintf('%.6F', $json['creationTime'])),
+            'creationTime' => \DateTimeImmutable::createFromFormat('U.u', \sprintf('%.6F', $json['creationTime'])) ?: throw new UnparsableResponse('Invalid timestamp received.'),
         ]);
     }
 }
diff --git a/src/Service/Ses/CHANGELOG.md b/src/Service/Ses/CHANGELOG.md
@@ -6,6 +6,10 @@
 
 - AWS api-change: Amazon SES now supports per-message tracking overrides. You can use the new ConfigurationOverrides parameter in SendEmail and SendBulkEmail to enable or disable open and click tracking for individual messages without changing your account-level or configuration set settings.
 
+### Changed
+
+- Throw `UnparsableResponse` instead of a `TypeError` when a required timestamp cannot be parsed
+
 ## 1.16.0
 
 ### Added

diff --git a/src/Service/Ses/src/Result/GetSuppressedDestinationResponse.php b/src/Service/Ses/src/Result/GetSuppressedDestinationResponse.php
@@ -2,6 +2,7 @@
 
 namespace AsyncAws\Ses\Result;
 
+use AsyncAws\Core\Exception\UnparsableResponse;
 use AsyncAws\Core\Response;
 use AsyncAws\Core\Result;
 use AsyncAws\Ses\Enum\SuppressionListReason;
@@ -39,7 +40,7 @@ private function populateResultSuppressedDestination(array $json): SuppressedDes
         return new SuppressedDestination([
             'EmailAddress' => (string) $json['EmailAddress'],
             'Reason' => !SuppressionListReason::exists((string) $json['Reason']) ? SuppressionListReason::UNKNOWN_TO_SDK : (string) $json['Reason'],
-            'LastUpdateTime' => /** @var \DateTimeImmutable $d */ $d = \DateTimeImmutable::createFromFormat('U.u', \sprintf('%.6F', $json['LastUpdateTime'])),
+            'LastUpdateTime' => \DateTimeImmutable::createFromFormat('U.u', \sprintf('%.6F', $json['LastUpdateTime'])) ?: throw new UnparsableResponse('Invalid timestamp received.'),
             'Attributes' => empty($json['Attributes']) ? null : $this->populateResultSuppressedDestinationAttributes($json['Attributes']),
             'TenantName' => isset($json['TenantName']) ? (string) $json['TenantName'] : null,
         ]);

diff --git a/src/Service/StepFunctions/CHANGELOG.md b/src/Service/StepFunctions/CHANGELOG.md
@@ -2,6 +2,10 @@
 
 ## NOT RELEASED
 
+### Changed
+
+- Throw `UnparsableResponse` instead of a `TypeError` when a required timestamp cannot be parsed
+
 ## 1.7.1
 
 ### Changed

diff --git a/src/Service/StepFunctions/src/Result/StartExecutionOutput.php b/src/Service/StepFunctions/src/Result/StartExecutionOutput.php
@@ -2,6 +2,7 @@
 
 namespace AsyncAws\StepFunctions\Result;
 
+use AsyncAws\Core\Exception\UnparsableResponse;
 use AsyncAws\Core\Response;
 use AsyncAws\Core\Result;
 
@@ -40,6 +41,6 @@ protected function populateResult(Response $response): void
         $data = $response->toArray();
 
         $this->executionArn = (string) $data['executionArn'];
-        $this->startDate = /** @var \DateTimeImmutable $d */ $d = \DateTimeImmutable::createFromFormat('U.u', \sprintf('%.6F', $data['startDate']));
+        $this->startDate = \DateTimeImmutable::createFromFormat('U.u', \sprintf('%.6F', $data['startDate'])) ?: throw new UnparsableResponse('Invalid timestamp received.');
     }
 }