diff --git a/internal/client/transport/http_reader.go b/internal/client/transport/http_reader.go
index dca5c17ac..b55746f06 100644
--- a/internal/client/transport/http_reader.go
+++ b/internal/client/transport/http_reader.go
@@ -19,7 +19,7 @@ import (
 )
 
 var (
-	contentRangeRegexp = regexp.MustCompile(`bytes ([0-9]+)-([0-9]+)/([0-9]+|\\*)`)
+	contentRangeRegexp = regexp.MustCompile(`^bytes ([0-9]+)-([0-9]+)/([0-9]+|\*)$`)
 
 	// ErrWrongCodeForByteRange is returned if the client sends a request
 	// with a Range header but the server returns a 2xx or 3xx code other
diff --git a/internal/client/transport/http_reader_test.go b/internal/client/transport/http_reader_test.go
index d97a51300..3be75adeb 100644
--- a/internal/client/transport/http_reader_test.go
+++ b/internal/client/transport/http_reader_test.go
@@ -145,3 +145,44 @@ func TestContentEncoding(t *testing.T) {
 		})
 	}
 }
+
+func TestSeekWithUnknownTotalSize(t *testing.T) {
+	t.Parallel()
+
+	content := make([]byte, 128)
+	rand.New(rand.NewSource(1)).Read(content)
+
+	s := httptest.NewServer(http.HandlerFunc(func(rw http.ResponseWriter, r *http.Request) {
+		// Respond to a range request with a 206 whose Content-Range
+		// reports an unknown complete length ("*"), as permitted by
+		// RFC 7233.
+		var start int
+		if _, err := fmt.Sscanf(r.Header.Get("Range"), "bytes=%d-", &start); err != nil || start < 0 || start > len(content) {
+			rw.WriteHeader(http.StatusBadRequest)
+			return
+		}
+		rw.Header().Set("Content-Range", fmt.Sprintf("bytes %d-%d/*", start, len(content)-1))
+		rw.Header().Set("Content-Length", fmt.Sprintf("%d", len(content)-start))
+		rw.WriteHeader(http.StatusPartialContent)
+		_, _ = rw.Write(content[start:])
+	}))
+	defer s.Close()
+
+	rs := NewHTTPReadSeeker(t.Context(), http.DefaultClient, s.URL, func(r *http.Response) error { return nil })
+	defer rs.Close()
+
+	const offset = 64
+	if _, err := rs.Seek(offset, io.SeekStart); err != nil {
+		t.Fatal(err)
+	}
+
+	b, err := io.ReadAll(rs)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	expected := content[offset:]
+	if !bytes.Equal(b, expected) {
+		t.Errorf("unexpected content: got %d bytes, expected %d", len(b), len(expected))
+	}
+}