diff --git a/.github/workflows/go.yml b/.github/workflows/go.yml
index 7e26840f0..79ea533b5 100644
--- a/.github/workflows/go.yml
+++ b/.github/workflows/go.yml
@@ -104,7 +104,7 @@ jobs:
       - name: Run multipart listing, cancellation and cleanup tests under race detector
         env:
           MINIO_API_REQUESTS_MAX: "10000"
-        run: go test -race ./cmd -run '^Test(Multipart|PaginateMultipartUploads|ListMultipartUploads|CleanupStaleUploads|ExtractModTime)' -count=1 -timeout=5m
+        run: go test -race ./cmd -run '^Test(ObjectCompleteMultipartUpload|Multipart|PaginateMultipartUploads|ListMultipartUploads|CleanupStaleUploads|ExtractModTime)' -count=1 -timeout=5m
 
       - name: Run listing metadata recovery, pagination and cancellation tests under race detector
         run: go test -race ./cmd -run '^Test(ListFallback|ListingCache|ListingMerge|ListingRecovery|ListingPending|ListingEntry|ListingSecondLock|StreamMetadataParts|LocalLockerListing|DistributedListing|MergeXLV2LatestNullCrossParity|CountXLV2MixedECGroups|ListCrossParity|ListObjectVersionsCrossParityNull|MigrationCrossParity)' -count=1 -timeout=5m
diff --git a/cmd/erasure-server-pool.go b/cmd/erasure-server-pool.go
index 0fac42c79..c17c45518 100644
--- a/cmd/erasure-server-pool.go
+++ b/cmd/erasure-server-pool.go
@@ -2419,13 +2419,17 @@ func (z *erasureServerPools) CompleteMultipartUpload(ctx context.Context, bucket
 
 	// Hold write locks to verify uploaded parts, also disallows any
 	// parallel PutObjectPart() requests.
-	uploadIDLock := z.NewNSLock(bucket, pathJoin(object, uploadID))
-	wlkctx, err := uploadIDLock.GetLock(ctx, globalOperationTimeout)
-	if err != nil {
-		return objInfo, err
+	// An empty upload ID aliases the object lock already held above.
+	// Let the storage layer return its normal missing bucket/upload error.
+	if uploadID != "" {
+		uploadIDLock := z.NewNSLock(bucket, pathJoin(object, uploadID))
+		wlkctx, err := uploadIDLock.GetLock(ctx, globalOperationTimeout)
+		if err != nil {
+			return objInfo, err
+		}
+		ctx = wlkctx.Context()
+		defer uploadIDLock.Unlock(wlkctx)
 	}
-	ctx = wlkctx.Context()
-	defer uploadIDLock.Unlock(wlkctx)
 
 	if z.SinglePool() {
 		return z.serverPools[0].CompleteMultipartUpload(ctx, bucket, object, uploadID, uploadedParts, opts)
diff --git a/cmd/restore-native_test.go b/cmd/restore-native_test.go
index 577607ced..706dbc8a4 100644
--- a/cmd/restore-native_test.go
+++ b/cmd/restore-native_test.go
@@ -707,3 +707,35 @@ func (r *nativeRestorePartGateReader) Read(p []byte) (int, error) {
 	}
 	return r.ReadCloser.Read(p)
 }
+
+// Invalid upload paths must retain the backend's normal error precedence,
+// rather than reacquiring the object lock as the upload lock.
+func TestMultipartCompletionLockAlias(t *testing.T) {
+	for _, pools := range []int{1, 2} {
+		for _, id := range []string{"", ".", "./"} {
+			t.Run(fmt.Sprintf("pools=%d/id=%q", pools, id), func(t *testing.T) {
+				r := newRestoreSafetyTest(t, pools, versioning.Enabled)
+				for _, missingBucket := range []bool{false, true} {
+					bucket := r.bucket
+					if missingBucket {
+						bucket = "missing-bucket"
+					}
+					ctx, cancel := context.WithTimeout(t.Context(), 200*time.Millisecond)
+					_, err := r.z.CompleteMultipartUpload(ctx, bucket, r.object, id, nil, ObjectOptions{})
+					cancel()
+					if id != "" {
+						if !errors.As(err, &MalformedUploadID{}) {
+							t.Errorf("malformed upload: %v", err)
+						}
+					} else if missingBucket {
+						if !isErrBucketNotFound(err) {
+							t.Errorf("missing bucket: %v", err)
+						}
+					} else if !errors.As(err, &InvalidUploadID{}) {
+						t.Errorf("invalid upload: %v", err)
+					}
+				}
+			})
+		}
+	}
+}