diff --git a/apps/files_external/lib/Lib/Backend/AmazonS3.php b/apps/files_external/lib/Lib/Backend/AmazonS3.php
index e345ed53f70..f71ca40cdfc 100644
--- a/apps/files_external/lib/Lib/Backend/AmazonS3.php
+++ b/apps/files_external/lib/Lib/Backend/AmazonS3.php
@@ -41,6 +41,9 @@ class AmazonS3 extends Backend {
 				(new DefinitionParameter('useMultipartCopy', $l->t('Enable multipart copy')))
 					->setType(DefinitionParameter::VALUE_BOOLEAN)
 					->setDefaultValue(true),
+				(new DefinitionParameter('sse_c_key', $l->t('SSE-C encryption key')))
+					->setType(DefinitionParameter::VALUE_PASSWORD)
+					->setFlag(DefinitionParameter::FLAG_OPTIONAL),
 			])
 			->addAuthScheme(AccessKey::SCHEME_AMAZONS3_ACCESSKEY)
 			->addAuthScheme(AuthMechanism::SCHEME_NULL)
diff --git a/apps/files_external/lib/Lib/Storage/AmazonS3.php b/apps/files_external/lib/Lib/Storage/AmazonS3.php
index 03a365fd559..1a866e8c22b 100644
--- a/apps/files_external/lib/Lib/Storage/AmazonS3.php
+++ b/apps/files_external/lib/Lib/Storage/AmazonS3.php
@@ -113,7 +113,7 @@ class AmazonS3 extends Common {
 				$this->objectCache[$key] = $this->getConnection()->headObject([
 					'Bucket' => $this->bucket,
 					'Key' => $key
-				])->toArray();
+				] + $this->getSSECParameters())->toArray();
 			} catch (S3Exception $e) {
 				if ($e->getStatusCode() >= 500) {
 					throw $e;
@@ -207,7 +207,7 @@ class AmazonS3 extends Common {
 				'Key' => $path . '/',
 				'Body' => '',
 				'ContentType' => FileInfo::MIMETYPE_FOLDER
-			]);
+			] + $this->getSSECParameters());
 			$this->testTimeout();
 		} catch (S3Exception $e) {
 			$this->logger->error($e->getMessage(), [
@@ -507,7 +507,7 @@ class AmazonS3 extends Common {
 				'Body' => '',
 				'ContentType' => $mimeType,
 				'MetadataDirective' => 'REPLACE',
-			]);
+			] + $this->getSSECParameters());
 			$this->testTimeout();
 		} catch (S3Exception $e) {
 			$this->logger->error($e->getMessage(), [
diff --git a/lib/private/Files/ObjectStore/S3ConnectionTrait.php b/lib/private/Files/ObjectStore/S3ConnectionTrait.php
index cce8752c360..65fc61ffa77 100644
--- a/lib/private/Files/ObjectStore/S3ConnectionTrait.php
+++ b/lib/private/Files/ObjectStore/S3ConnectionTrait.php
@@ -213,7 +213,7 @@ trait S3ConnectionTrait {
 	}
 
 	protected function getSSECKey(): ?string {
-		if (isset($this->params['sse_c_key'])) {
+		if (isset($this->params['sse_c_key']) && !empty($this->params['sse_c_key'])) {
 			return $this->params['sse_c_key'];
 		}