diff --git a/src/database/database.cpp b/src/database/database.cpp
index ec4df5f8..e826f576 100644
--- a/src/database/database.cpp
+++ b/src/database/database.cpp
@@ -51,7 +51,7 @@ static SingletonEnv<leveldb::EspEnv> sEnv;
 static const char kDbPath[] = "/.tangara-db";
 
 static const char kKeyDbVersion[] = "schema_version";
-static const uint8_t kCurrentDbVersion = 4;
+static const uint8_t kCurrentDbVersion = 3;
 static const char kKeyCollator[] = "collator";
 static const char kKeyTrackId[] = "next_track_id";
 
diff --git a/src/database/index.cpp b/src/database/index.cpp
index 1548a3be..7d556192 100644
--- a/src/database/index.cpp
+++ b/src/database/index.cpp
@@ -8,7 +8,6 @@
 
 #include <cstdint>
 #include <sstream>
-#include <string>
 #include <variant>
 
 #include "collation.hpp"
@@ -56,7 +55,7 @@ static auto missing_component_text(const Track& track, Tag tag)
     case Tag::kTitle:
       return track.TitleOrFilename();
     case Tag::kAlbumTrack:
-      return "0";
+      return "0000";
     case Tag::kDuration:
     default:
       return {};
@@ -77,29 +76,17 @@ auto Index(locale::ICollator& collator, const IndexInfo& info, const Track& t)
   };
 
   for (std::uint8_t i = 0; i < info.components.size(); i++) {
-    Tag component = info.components.at(i);
     // Fill in the text for this depth.
+    auto text = t.tags().at(info.components.at(i));
     std::pmr::string value;
-
-    if (component == Tag::kAlbumTrack) {
-      // Track numbers are a special case, since they're numbers rather than
-      // text.
-      auto pmr_num = t.tags().at(component).value_or("0");
-      // std::pmr continues to be a true disappointment.
-      std::string raw_num{pmr_num.data(), pmr_num.size()};
-      uint32_t num = std::stoi(raw_num);
-      key.item = std::pmr::string{reinterpret_cast<char*>(&num), 4};
+    if (text) {
+      std::pmr::string orig = *text;
+      auto xfrm = collator.Transform({orig.data(), orig.size()});
+      key.item = {xfrm.data(), xfrm.size()};
+      value = *text;
     } else {
-      auto text = t.tags().at(component);
-      if (text) {
-        std::pmr::string orig = *text;
-        auto xfrm = collator.Transform({orig.data(), orig.size()});
-        key.item = {xfrm.data(), xfrm.size()};
-        value = *text;
-      } else {
-        key.item = {};
-        value = missing_component_text(t, info.components.at(i)).value_or("");
-      }
+      key.item = {};
+      value = missing_component_text(t, info.components.at(i)).value_or("");
     }
 
     // If this is the last component, then we should also fill in the track id
diff --git a/src/database/tag_parser.cpp b/src/database/tag_parser.cpp
index 44377074..eb5f3a43 100644
--- a/src/database/tag_parser.cpp
+++ b/src/database/tag_parser.cpp
@@ -30,8 +30,9 @@ const static std::array<std::pair<const char*, Tag>, 5> kVorbisIdToTag = {{
 }};
 
 static auto convert_track_number(int number) -> std::pmr::string {
-  std::string s = std::to_string(number);
-  return {s.data(), s.size()};
+  std::ostringstream oss;
+  oss << std::setw(4) << std::setfill('0') << number;
+  return std::pmr::string(oss.str());
 }
 
 static auto convert_track_number(const std::pmr::string& raw)
@@ -166,7 +167,8 @@ auto TagParserImpl::ReadAndParseTags(const std::pmr::string& path)
     }
   }
 
-  // Normalise track numbers to ensure that they're actually numbers.
+  // Normalise track numbers; they're usually treated as strings, but we would
+  // like to sort them lexicographically.
   tags->set(Tag::kAlbumTrack,
             convert_track_number(tags->at(Tag::kAlbumTrack).value_or("0")));