diff --git a/pkg/rsstorage/servers/s3server/s3_encrypted_service.go b/pkg/rsstorage/servers/s3server/s3_encrypted_service.go
index 83b0025..faec1d0 100644
--- a/pkg/rsstorage/servers/s3server/s3_encrypted_service.go
+++ b/pkg/rsstorage/servers/s3server/s3_encrypted_service.go
@@ -115,3 +115,7 @@ func (s *encryptedS3Service) GetObject(input *s3.GetObjectInput) (*s3.GetObjectO
 	}
 	return out, err
 }
+
+func (s *encryptedS3Service) KmsEncrypted() bool {
+	return true
+}
diff --git a/pkg/rsstorage/servers/s3server/s3_service.go b/pkg/rsstorage/servers/s3server/s3_service.go
index c6bc6b7..ce4d324 100644
--- a/pkg/rsstorage/servers/s3server/s3_service.go
+++ b/pkg/rsstorage/servers/s3server/s3_service.go
@@ -30,6 +30,7 @@ type S3Wrapper interface {
 	CopyObject(bucket, key, newBucket, newKey string) (*s3.CopyObjectOutput, error)
 	MoveObject(bucket, key, newBucket, newKey string) (*s3.CopyObjectOutput, error)
 	ListObjects(bucket, prefix string) ([]string, error)
+	KmsEncrypted() bool
 }
 
 type defaultS3Wrapper struct {
@@ -57,6 +58,10 @@ func NewS3Wrapper(configInput *rsstorage.ConfigS3, keyID string) (S3Wrapper, err
 	}, nil
 }
 
+func (s *defaultS3Wrapper) KmsEncrypted() bool {
+	return false
+}
+
 func (s *defaultS3Wrapper) CreateBucket(input *s3.CreateBucketInput) (*s3.CreateBucketOutput, error) {
 	svc := s3.New(s.session)
 	out, err := svc.CreateBucket(input)
diff --git a/pkg/rsstorage/servers/s3server/server.go b/pkg/rsstorage/servers/s3server/server.go
index 409c377..4530f80 100644
--- a/pkg/rsstorage/servers/s3server/server.go
+++ b/pkg/rsstorage/servers/s3server/server.go
@@ -9,6 +9,7 @@ import (
 	"io"
 	"net/url"
 	"path/filepath"
+	"strconv"
 	"strings"
 	"time"
 
@@ -23,6 +24,8 @@ import (
 	"github.com/rstudio/platform-lib/pkg/rsstorage/types"
 )
 
+const AmzUnencryptedContentLengthHeader = "X-Amz-Unencrypted-Content-Length"
+
 type moveOrCopyFn func(bucket, key, newBucket, newKey string) (*s3.CopyObjectOutput, error)
 
 type StorageServer struct {
@@ -107,6 +110,7 @@ func (s *StorageServer) Validate() error {
 
 func (s *StorageServer) Check(dir, address string) (bool, *types.ChunksInfo, int64, time.Time, error) {
 	var chunked bool
+	var contentLength int64
 	addr := internal.NotEmptyJoin([]string{s.prefix, dir, address}, "/")
 	infoAddr := filepath.Join(addr, "info.json")
 	resp, err := s.svc.HeadObject(&s3.HeadObjectInput{Bucket: aws.String(s.bucket), Key: aws.String(addr)})
@@ -152,8 +156,17 @@ func (s *StorageServer) Check(dir, address string) (bool, *types.ChunksInfo, int
 		}
 		return true, &info, int64(info.FileSize), info.ModTime, nil
 	} else {
+		// Check some headers for the unencrypted content length for KMS encrypted objects.
+		if s.svc.KmsEncrypted() {
+			if cl, ok := resp.Metadata[AmzUnencryptedContentLengthHeader]; ok {
+				contentLength, _ = strconv.ParseInt(*cl, 10, 64)
+			}
+		} else {
+			contentLength = *resp.ContentLength
+		}
+
 		// For standard assets, the HeadObject response has the information we need.
-		return true, nil, *resp.ContentLength, *resp.LastModified, nil
+		return true, nil, contentLength, *resp.LastModified, nil
 	}
 }
 
@@ -172,6 +185,7 @@ func (s *StorageServer) CalculateUsage() (types.Usage, error) {
 
 func (s *StorageServer) Get(dir, address string) (io.ReadCloser, *types.ChunksInfo, int64, time.Time, bool, error) {
 	var chunked bool
+	var contentLength int64
 	addr := internal.NotEmptyJoin([]string{s.prefix, dir, address}, "/")
 	infoAddr := filepath.Join(addr, "info.json")
 	resp, err := s.svc.GetObject(&s3.GetObjectInput{Bucket: aws.String(s.bucket), Key: aws.String(addr)})
@@ -208,8 +222,17 @@ func (s *StorageServer) Get(dir, address string) (io.ReadCloser, *types.ChunksIn
 		}
 		return r, c, sz, mod, true, nil
 	} else {
+		// Check some headers for the unencrypted content length for KMS encrypted objects.
+		if s.svc.KmsEncrypted() {
+			if cl, ok := resp.Metadata[AmzUnencryptedContentLengthHeader]; ok {
+				contentLength, _ = strconv.ParseInt(*cl, 10, 64)
+			}
+		} else {
+			contentLength = *resp.ContentLength
+		}
+
 		// For standard assets, the GetObject response has the information we need.
-		return resp.Body, nil, *resp.ContentLength, *resp.LastModified, true, nil
+		return resp.Body, nil, contentLength, *resp.LastModified, true, nil
 	}
 }
 
diff --git a/pkg/rsstorage/servers/s3server/server_test.go b/pkg/rsstorage/servers/s3server/server_test.go
index 96a73cb..85b8cdd 100644
--- a/pkg/rsstorage/servers/s3server/server_test.go
+++ b/pkg/rsstorage/servers/s3server/server_test.go
@@ -78,6 +78,10 @@ type fakeS3 struct {
 	delBucketOut *s3.DeleteBucketOutput
 }
 
+func (s *fakeS3) KmsEncrypted() bool {
+	return false
+}
+
 func (s *fakeS3) CreateBucket(input *s3.CreateBucketInput) (*s3.CreateBucketOutput, error) {
 	if s.bucketErr == nil {
 		s.bucketIn = input