diff --git a/implementations/c/preserves.h b/implementations/c/preserves.h
index c80d71a..446b21d 100644
--- a/implementations/c/preserves.h
+++ b/implementations/c/preserves.h
@@ -284,6 +284,7 @@ typedef enum preserves_type_tag {
   PRESERVES_SIGNED_INTEGER,
   PRESERVES_STRING,
   PRESERVES_BYTE_STRING,
+  PRESERVES_COMPACT,
   PRESERVES_SYMBOL,
 
   PRESERVES_RECORD,
@@ -304,6 +305,7 @@ PRESERVES_OUTOFLINE(char const *preserves_type_tag_name(preserves_type_tag_t typ
       case PRESERVES_SIGNED_INTEGER: return "SIGNED_INTEGER";
       case PRESERVES_STRING: return "STRING";
       case PRESERVES_BYTE_STRING: return "BYTE_STRING";
+      case PRESERVES_COMPACT: return "COMPACT";
       case PRESERVES_SYMBOL: return "SYMBOL";
       case PRESERVES_RECORD: return "RECORD";
       case PRESERVES_SEQUENCE: return "SEQUENCE";
@@ -397,6 +399,8 @@ PRESERVES_OUTOFLINE
       that need ByteString-style backslash-escapes interpreted
     - repr=PRESERVES_HEX -> len, data._unsigned as absolute offset within input to ASCII bytes of hex
     - repr=PRESERVES_BASE64 -> len, data._unsigned as absolute offset within input to ASCII bytes of base64
+  PRESERVES_COMPACT:
+    - repr as for BYTE_STRING, but bytes denote a nested binary-encoded value.
   PRESERVES_SYMBOL:
     - repr=PRESERVES_LITERAL -> len, data._unsigned as absolute offset within input to utf-8 bytes
     - repr=PRESERVES_ESCAPED -> len, data._unsigned as absolute offset within input to utf-8 bytes
@@ -736,7 +740,8 @@ PRESERVES_IMPLEMENTATION_CHUNK
 
  static inline preserves_error_code_t _preserves_reader_read_stringlike(preserves_reader_t *r,
                                                                         size_t *count_ptr,
-                                                                        preserves_type_tag_t type) {
+                                                                        preserves_type_tag_t type,
+                                                                        bool should_check_utf8) {
    size_t len = 0;
    switch (_preserves_reader_varint(r, &len)) {
      case -1: return PRESERVES_END_INCOMPLETE_INPUT;
@@ -745,7 +750,7 @@ PRESERVES_IMPLEMENTATION_CHUNK
    }
    size_t starting_pos = r->input_pos;
    uint8_t *maybe_utf = _preserves_reader_next_bytes(r, len);
-   if ((type != PRESERVES_BYTE_STRING) && (check_utf8(maybe_utf, len) == -1)) {
+   if (should_check_utf8 && (check_utf8(maybe_utf, len) == -1)) {
      return PRESERVES_END_INVALID_UTF8;
    }
    if (_preserves_reader_emit_entry(r, count_ptr, (preserves_index_entry_t) {
@@ -891,21 +896,21 @@ PRESERVES_OUTOFLINE
 
        case PRESERVES_BINARY_FORMAT_TAG_STRING: {
          preserves_error_code_t code =
-           _preserves_reader_read_stringlike(r, &count, PRESERVES_STRING);
+           _preserves_reader_read_stringlike(r, &count, PRESERVES_STRING, true);
          if (code != PRESERVES_END_NO_ERROR) return _preserves_reader_finish(r, code);
          break;
        }
 
        case PRESERVES_BINARY_FORMAT_TAG_BYTE_STRING: {
          preserves_error_code_t code =
-           _preserves_reader_read_stringlike(r, &count, PRESERVES_BYTE_STRING);
+           _preserves_reader_read_stringlike(r, &count, PRESERVES_BYTE_STRING, false);
          if (code != PRESERVES_END_NO_ERROR) return _preserves_reader_finish(r, code);
          break;
        }
 
        case PRESERVES_BINARY_FORMAT_TAG_SYMBOL: {
          preserves_error_code_t code =
-           _preserves_reader_read_stringlike(r, &count, PRESERVES_SYMBOL);
+           _preserves_reader_read_stringlike(r, &count, PRESERVES_SYMBOL, true);
          if (code != PRESERVES_END_NO_ERROR) return _preserves_reader_finish(r, code);
          break;
        }
@@ -1022,6 +1027,7 @@ PRESERVES_IMPLEMENTATION_CHUNK
 
      case PRESERVES_STRING:
      case PRESERVES_BYTE_STRING:
+     case PRESERVES_COMPACT:
      case PRESERVES_SYMBOL: {
        fprintf(f, " offset %lu ", i->data._unsigned);
        preserves_bytes_t data = preserves_bytes_subsequence(input, i->data._unsigned, i->len);