diff --git a/gpt4all-backend/tokenizer/bpe.h b/gpt4all-backend/tokenizer/bpe.h
index 3e43dd22..e53c1323 100644
--- a/gpt4all-backend/tokenizer/bpe.h
+++ b/gpt4all-backend/tokenizer/bpe.h
@@ -88,7 +88,7 @@ struct buf_ref {
     uint32_t offset : 20;
     uint32_t length : 12;
 
-    std::string_view into(const char* buf) {
+    std::string_view into(const char* buf) const {
         return std::string_view(&buf[offset], length);
     }
 };