diff --git a/vendor/hayro-cmap/src/lib.rs b/vendor/hayro-cmap/src/lib.rs
index c45cc0ae54..4eb88f5053 100644
--- a/vendor/hayro-cmap/src/lib.rs
+++ b/vendor/hayro-cmap/src/lib.rs
@@ -1125,6 +1125,18 @@ endbfchar
         assert!(CMap::parse(b"<00", |_| None).is_none());
     }
 
+    #[test]
+    fn truncated_stream_with_only_metadata_reports_failure() {
+        // Character-collection metadata alone is not a usable CMap: an empty
+        // metadata-only map would block the caller's fallback paths, so a
+        // truncated stream with no mappings must report failure here too.
+        assert!(CMap::parse(
+            b"/Registry (Adobe) /Ordering (Japan1) /Supplement 0 <00",
+            |_| None
+        )
+        .is_none());
+    }
+
     #[test]
     fn bad_bfchar_code_keeps_later_entries_aligned() {
         // The malformed 5-byte code still has a destination object; both
diff --git a/vendor/hayro-cmap/src/parse.rs b/vendor/hayro-cmap/src/parse.rs
index 9450bbbe2d..2a89fdbac7 100644
--- a/vendor/hayro-cmap/src/parse.rs
+++ b/vendor/hayro-cmap/src/parse.rs
@@ -154,7 +154,6 @@ pub(crate) fn parse_inner<'a>(
         && notdef_ranges.is_empty()
         && bf_entries.is_empty()
         && base.is_none()
-        && metadata.character_collection.is_none()
     {
         return None;
     }