diff --git a/storage/grpc_client.go b/storage/grpc_client.go
index 6a997befc061..1dfb6f8302be 100644
--- a/storage/grpc_client.go
+++ b/storage/grpc_client.go
@@ -34,7 +34,6 @@ import (
 	"google.golang.org/grpc/codes"
 	"google.golang.org/grpc/metadata"
 	"google.golang.org/grpc/status"
-	"google.golang.org/protobuf/proto"
 	fieldmaskpb "google.golang.org/protobuf/types/known/fieldmaskpb"
 )
 
@@ -1500,23 +1499,10 @@ func (w *gRPCWriter) startResumableUpload() error {
 		WriteObjectSpec:           spec,
 		CommonObjectRequestParams: toProtoCommonObjectRequestParams(w.encryptionKey),
 	}
-	// TODO: Currently the checksums are only sent on the first message
-	// of the stream, but in the future, we must also support sending it
-	// on the *last* message of the stream (instead of the first).
-	if w.sendCRC32C {
-		req.ObjectChecksums = &storagepb.ObjectChecksums{
-			Crc32C: proto.Uint32(w.attrs.CRC32C),
-		}
-	}
-	if len(w.attrs.MD5) != 0 {
-		if cs := req.GetObjectChecksums(); cs == nil {
-			req.ObjectChecksums = &storagepb.ObjectChecksums{
-				Md5Hash: w.attrs.MD5,
-			}
-		} else {
-			cs.Md5Hash = w.attrs.MD5
-		}
-	}
+	// TODO: Currently the checksums are only sent on the request to initialize
+	// the upload, but in the future, we must also support sending it
+	// on the *last* message of the stream.
+	req.ObjectChecksums = toProtoChecksums(w.sendCRC32C, w.attrs)
 	return run(w.ctx, func() error {
 		upres, err := w.c.raw.StartResumableWrite(w.ctx, req)
 		w.upid = upres.GetUploadId()
@@ -1603,6 +1589,11 @@ func (w *gRPCWriter) uploadBuffer(recvd int, start int64, doneReading bool) (*st
 					WriteObjectSpec: spec,
 				}
 				req.CommonObjectRequestParams = toProtoCommonObjectRequestParams(w.encryptionKey)
+				// For a non-resumable upload, checksums must be sent in this message.
+				// TODO: Currently the checksums are only sent on the first message
+				// of the stream, but in the future, we must also support sending it
+				// on the *last* message of the stream (instead of the first).
+				req.ObjectChecksums = toProtoChecksums(w.sendCRC32C, w.attrs)
 			}
 
 		}
diff --git a/storage/integration_test.go b/storage/integration_test.go
index 9d9f3158975d..eb5b27557d20 100644
--- a/storage/integration_test.go
+++ b/storage/integration_test.go
@@ -2695,7 +2695,7 @@ func TestIntegration_HashesOnUpload(t *testing.T) {
 		w.CRC32C = crc32c
 		w.SendCRC32C = true
 		if err := write(w); err != nil {
-			t.Fatal(err)
+			t.Error(err)
 		}
 
 		// If we change the CRC, validation should fail.
@@ -2703,14 +2703,14 @@ func TestIntegration_HashesOnUpload(t *testing.T) {
 		w.CRC32C = crc32c + 1
 		w.SendCRC32C = true
 		if err := write(w); err == nil {
-			t.Fatal("write with bad CRC32c: want error, got nil")
+			t.Error("write with bad CRC32c: want error, got nil")
 		}
 
 		// If we have the wrong CRC but forget to send it, we succeed.
 		w = obj.NewWriter(ctx)
 		w.CRC32C = crc32c + 1
 		if err := write(w); err != nil {
-			t.Fatal(err)
+			t.Error(err)
 		}
 
 		// MD5
@@ -2719,7 +2719,7 @@ func TestIntegration_HashesOnUpload(t *testing.T) {
 		w = obj.NewWriter(ctx)
 		w.MD5 = md5[:]
 		if err := write(w); err != nil {
-			t.Fatal(err)
+			t.Error(err)
 		}
 
 		// If we change the MD5, validation should fail.
@@ -2727,7 +2727,7 @@ func TestIntegration_HashesOnUpload(t *testing.T) {
 		w.MD5 = append([]byte(nil), md5[:]...)
 		w.MD5[0]++
 		if err := write(w); err == nil {
-			t.Fatal("write with bad MD5: want error, got nil")
+			t.Error("write with bad MD5: want error, got nil")
 		}
 	})
 }
diff --git a/storage/storage.go b/storage/storage.go
index b5c10efc8a75..c4a771593249 100644
--- a/storage/storage.go
+++ b/storage/storage.go
@@ -2079,6 +2079,25 @@ func toProtoCommonObjectRequestParams(key []byte) *storagepb.CommonObjectRequest
 	}
 }
 
+func toProtoChecksums(sendCRC32C bool, attrs *ObjectAttrs) *storagepb.ObjectChecksums {
+	var checksums *storagepb.ObjectChecksums
+	if sendCRC32C {
+		checksums = &storagepb.ObjectChecksums{
+			Crc32C: proto.Uint32(attrs.CRC32C),
+		}
+	}
+	if len(attrs.MD5) != 0 {
+		if checksums == nil {
+			checksums = &storagepb.ObjectChecksums{
+				Md5Hash: attrs.MD5,
+			}
+		} else {
+			checksums.Md5Hash = attrs.MD5
+		}
+	}
+	return checksums
+}
+
 // ServiceAccount fetches the email address of the given project's Google Cloud Storage service account.
 func (c *Client) ServiceAccount(ctx context.Context, projectID string) (string, error) {
 	o := makeStorageOpts(true, c.retry, "")