diff --git a/internal/catalog/lookup_key.go b/internal/catalog/lookup_key.go
index 4d45d85..43ed849 100644
--- a/internal/catalog/lookup_key.go
+++ b/internal/catalog/lookup_key.go
@@ -3,7 +3,7 @@ package catalog
 import "strings"
 
 // TrackLookupKey builds a normalized cache key for entity resolution.
-// Uses null-byte separators to avoid collisions between field values.
+// Uses unit separator (U+001F) to avoid collisions between field values.
 func TrackLookupKey(artist, track, album string) string {
-	return strings.ToLower(artist) + "\x00" + strings.ToLower(track) + "\x00" + strings.ToLower(album)
+	return strings.ToLower(artist) + "\x1f" + strings.ToLower(track) + "\x1f" + strings.ToLower(album)
 }