diff --git a/spacy/tokens/doc.pyx b/spacy/tokens/doc.pyx
index 7dfe0ca9f..3bc404dd0 100644
--- a/spacy/tokens/doc.pyx
+++ b/spacy/tokens/doc.pyx
@@ -544,10 +544,6 @@ cdef class Doc:
 
         DOCS: https://spacy.io/api/doc#char_span
         """
-        if not isinstance(label, int):
-            label = self.vocab.strings.add(label)
-        if not isinstance(kb_id, int):
-            kb_id = self.vocab.strings.add(kb_id)
         alignment_modes = ("strict", "contract", "expand")
         if alignment_mode not in alignment_modes:
             raise ValueError(