diff --git a/src/indexer.cc b/src/indexer.cc
index 913416f3..56d78211 100644
--- a/src/indexer.cc
+++ b/src/indexer.cc
@@ -1464,12 +1464,12 @@ void OnIndexDeclaration(CXClientData client_data, const CXIdxDeclInfo* decl) {
           IndexFuncId parent_func_id =
               db->ToFuncId(decl->semanticContainer->cursor);
           var->def.parent_kind = SymbolKind::Func;
-          var->def.parent_id = size_t(parent_func_id);
+          var->def.parent_id = Id<void>(parent_func_id);
         } else if (IsTypeDefinition(decl->semanticContainer)) {
           IndexTypeId parent_type_id =
               db->ToTypeId(decl->semanticContainer->cursor);
           var->def.parent_kind = SymbolKind::Type;
-          var->def.parent_id = size_t(parent_type_id);
+          var->def.parent_id = Id<void>(parent_type_id);
           db->Resolve(parent_type_id)->def.vars.push_back(var_id);
         }
       }
diff --git a/src/indexer.h b/src/indexer.h
index 295c0a99..37b1dd70 100644
--- a/src/indexer.h
+++ b/src/indexer.h
@@ -36,20 +36,22 @@ struct IndexVar;
 enum class SymbolKind : uint8_t { Invalid, File, Type, Func, Var };
 MAKE_REFLECT_TYPE_PROXY(SymbolKind);
 
+using RawId = uint32_t;
+
 template <typename T>
 struct Id {
-  size_t id;
+  RawId id;
 
   // Invalid id.
   Id() : id(-1) {}
-  explicit Id(size_t id) : id(id) {}
+  explicit Id(RawId id) : id(id) {}
   template <typename U>
   explicit Id(Id<U> o) : id(o.id) {}
 
   // Needed for google::dense_hash_map.
-  explicit operator size_t() const { return id; }
+  explicit operator RawId() const { return id; }
 
-  bool HasValue() const { return id != size_t(-1); }
+  bool HasValue() const { return id != RawId(-1); }
 
   bool operator==(const Id<T>& other) const { return id == other.id; }
 
@@ -99,7 +101,7 @@ struct IndexFuncRef {
   IndexFuncRef(IndexFuncId id, Range loc, bool is_implicit)
       : id(id), loc(loc), is_implicit(is_implicit) {}
   IndexFuncRef(Range loc, bool is_implicit)
-      : id(IndexFuncId((size_t)-1)), loc(loc), is_implicit(is_implicit) {}
+      : loc(loc), is_implicit(is_implicit) {}
 
   inline bool operator==(const IndexFuncRef& other) {
     return id == other.id && loc == other.loc &&
@@ -109,12 +111,11 @@ struct IndexFuncRef {
     return !(*this == other);
   }
   inline bool operator<(const IndexFuncRef& other) const {
-    if (id < other.id)
-      return true;
-    if (id == other.id && loc < other.loc)
-      return true;
-    return id == other.id && loc == other.loc &&
-           is_implicit < other.is_implicit;
+    if (id != other.id)
+      return id < other.id;
+    if (loc != other.loc)
+      return loc < other.loc;
+    return is_implicit < other.is_implicit;
   }
 };
 
@@ -144,12 +145,11 @@ inline void Reflect(Writer& visitor, IndexFuncRef& value) {
   if (value.is_implicit)
     s += "~";
 
-  // id.id is unsigned, special case 0 value
-  if (value.id.id == static_cast<size_t>(-1)) {
-    s += "-1";
-  } else {
+  // id.id is unsigned, special case -1 value
+  if (value.id.HasValue())
     s += std::to_string(value.id.id);
-  }
+  else
+    s += "-1";
 
   s += "@" + value.loc.ToString();
   visitor.String(s.c_str());
@@ -403,7 +403,7 @@ struct VarDefDefinitionData {
   Maybe<TypeId> variable_type;
 
   // Function/type which declares this one.
-  size_t parent_id = size_t(-1);
+  Maybe<Id<void>> parent_id;
   int16_t short_name_offset = 0;
   int16_t short_name_size = 0;
   SymbolKind parent_kind = SymbolKind::Invalid;
diff --git a/src/message_handler.cc b/src/message_handler.cc
index 0fc409fd..95c2bcc2 100644
--- a/src/message_handler.cc
+++ b/src/message_handler.cc
@@ -54,7 +54,7 @@ bool FindFileOrFail(QueryDatabase* db,
   }
 
   if (out_file_id)
-    *out_file_id = QueryFileId((size_t)-1);
+    *out_file_id = QueryFileId();
 
   bool indexing = project->absolute_path_to_entry_index_.find(absolute_path) !=
                   project->absolute_path_to_entry_index_.end();
diff --git a/src/query.cc b/src/query.cc
index 665c1a64..b681b1fc 100644
--- a/src/query.cc
+++ b/src/query.cc
@@ -304,7 +304,7 @@ Maybe<QueryFileId> GetQueryFileIdFromPath(QueryDatabase* query_db,
   if (!create_if_missing)
     return {};
 
-  size_t idx = query_db->files.size();
+  RawId idx = query_db->files.size();
   query_db->usr_to_file[normalized_path] = QueryFileId(idx);
   query_db->files.push_back(QueryFile(path));
   return QueryFileId(idx);
@@ -319,7 +319,7 @@ Maybe<QueryTypeId> GetQueryTypeIdFromUsr(QueryDatabase* query_db,
   if (!create_if_missing)
     return {};
 
-  size_t idx = query_db->types.size();
+  RawId idx = query_db->types.size();
   query_db->usr_to_type[usr] = QueryTypeId(idx);
   query_db->types.push_back(QueryType(usr));
   return QueryTypeId(idx);
@@ -334,7 +334,7 @@ Maybe<QueryFuncId> GetQueryFuncIdFromUsr(QueryDatabase* query_db,
   if (!create_if_missing)
     return {};
 
-  size_t idx = query_db->funcs.size();
+  RawId idx = query_db->funcs.size();
   query_db->usr_to_func[usr] = QueryFuncId(idx);
   query_db->funcs.push_back(QueryFunc(usr));
   return QueryFuncId(idx);
@@ -349,7 +349,7 @@ Maybe<QueryVarId> GetQueryVarIdFromUsr(QueryDatabase* query_db,
   if (!create_if_missing)
     return {};
 
-  size_t idx = query_db->vars.size();
+  RawId idx = query_db->vars.size();
   query_db->usr_to_var[usr] = QueryVarId(idx);
   query_db->vars.push_back(QueryVar(usr));
   return QueryVarId(idx);
@@ -956,15 +956,15 @@ void QueryDatabase::ImportOrUpdate(
 
 void QueryDatabase::UpdateSymbols(Maybe<Id<void>>* symbol_idx,
                                   SymbolKind kind,
-                                  size_t idx) {
+                                  RawId idx) {
   if (!symbol_idx->has_value()) {
     *symbol_idx = Id<void>(symbols.size());
     symbols.push_back(SymbolIdx(kind, idx));
   }
 }
 
-std::string_view QueryDatabase::GetSymbolDetailedName(size_t symbol_idx) const {
-  size_t idx = symbols[symbol_idx].idx;
+std::string_view QueryDatabase::GetSymbolDetailedName(RawId symbol_idx) const {
+  RawId idx = symbols[symbol_idx].idx;
   switch (symbols[symbol_idx].kind) {
     default:
       break;
@@ -988,8 +988,8 @@ std::string_view QueryDatabase::GetSymbolDetailedName(size_t symbol_idx) const {
   return "";
 }
 
-std::string_view QueryDatabase::GetSymbolShortName(size_t symbol_idx) const {
-  size_t idx = symbols[symbol_idx].idx;
+std::string_view QueryDatabase::GetSymbolShortName(RawId symbol_idx) const {
+  RawId idx = symbols[symbol_idx].idx;
   switch (symbols[symbol_idx].kind) {
     default:
       break;
diff --git a/src/query.h b/src/query.h
index 60df5141..91c008f2 100644
--- a/src/query.h
+++ b/src/query.h
@@ -61,12 +61,12 @@ struct hash<::SymbolKind> {
 
 struct SymbolIdx {
   SymbolKind kind;
-  size_t idx;
+  RawId idx;
 
   SymbolIdx()
       : kind(SymbolKind::Invalid),
-        idx((size_t)-1) {}  // Default ctor needed by stdlib. Do not use.
-  SymbolIdx(SymbolKind kind, uint64_t idx) : kind(kind), idx(idx) {}
+        idx(RawId(-1)) {}  // Default ctor needed by stdlib. Do not use.
+  SymbolIdx(SymbolKind kind, RawId idx) : kind(kind), idx(idx) {}
 
   bool operator==(const SymbolIdx& that) const {
     return kind == that.kind && idx == that.idx;
@@ -386,9 +386,9 @@ struct QueryDatabase {
   void ImportOrUpdate(const std::vector<QueryType::DefUpdate>& updates);
   void ImportOrUpdate(const std::vector<QueryFunc::DefUpdate>& updates);
   void ImportOrUpdate(const std::vector<QueryVar::DefUpdate>& updates);
-  void UpdateSymbols(Maybe<Id<void>>* symbol_idx, SymbolKind kind, size_t idx);
-  std::string_view GetSymbolDetailedName(size_t symbol_idx) const;
-  std::string_view GetSymbolShortName(size_t symbol_idx) const;
+  void UpdateSymbols(Maybe<Id<void>>* symbol_idx, SymbolKind kind, RawId idx);
+  std::string_view GetSymbolDetailedName(RawId symbol_idx) const;
+  std::string_view GetSymbolShortName(RawId symbol_idx) const;
 
   // Query the indexing structure to look up symbol id for given Usr.
   Maybe<QueryFileId> GetQueryFileIdFromPath(const std::string& path);