diff --git a/src/reader/spirv/parser_impl.cc b/src/reader/spirv/parser_impl.cc
index cbe0456..c440dc3 100644
--- a/src/reader/spirv/parser_impl.cc
+++ b/src/reader/spirv/parser_impl.cc
@@ -1033,10 +1033,17 @@
   if (num_non_writable_members == members.size()) {
     read_only_struct_types_.insert(result.ast->name());
   }
-  builder_.AST().AddConstructedType(result);
+  AddConstructedType(sym, result);
   return result;
 }
 
+void ParserImpl::AddConstructedType(Symbol name, typ::Type type) {
+  auto iter = constructed_types_.insert(name);
+  if (iter.second) {
+    builder_.AST().AddConstructedType(type);
+  }
+}
+
 typ::Type ParserImpl::ConvertType(uint32_t type_id,
                                   const spvtools::opt::analysis::Pointer*) {
   const auto* inst = def_use_mgr_->GetDef(type_id);
@@ -1202,11 +1209,11 @@
     return {};
   }
   const auto name = namer_.GetName(type_id);
-  auto ast_alias_type =
-      builder_.ty.alias(builder_.Symbols().Register(name), ast_underlying_type);
+  const auto sym = builder_.Symbols().Register(name);
+  auto ast_alias_type = builder_.ty.alias(sym, ast_underlying_type);
 
   // Record this new alias as the AST type for this SPIR-V ID.
-  builder_.AST().AddConstructedType(ast_alias_type);
+  AddConstructedType(sym, ast_alias_type);
 
   return ast_alias_type;
 }
diff --git a/src/reader/spirv/parser_impl.h b/src/reader/spirv/parser_impl.h
index 425e8e5..56e4afa 100644
--- a/src/reader/spirv/parser_impl.h
+++ b/src/reader/spirv/parser_impl.h
@@ -591,6 +591,11 @@
   bool ParseArrayDecorations(const spvtools::opt::analysis::Type* spv_type,
                              ast::DecorationList* decorations);
 
+  /// Adds `type` as a constructed type if it hasn't been added yet.
+  /// @param name the type's unique name
+  /// @param type the type to add
+  void AddConstructedType(Symbol name, typ::Type type);
+
   /// Creates a new `ast::Node` owned by the ProgramBuilder.
   /// @param args the arguments to pass to the type constructor
   /// @returns the node pointer
@@ -691,6 +696,10 @@
   std::unordered_map<const spvtools::opt::Instruction*, typ::Pointer>
       handle_type_;
 
+  // Set of symbols of constructed types that have been added, used to avoid
+  // adding duplicates.
+  std::unordered_set<Symbol> constructed_types_;
+
   /// Maps the SPIR-V ID of a module-scope builtin variable that should be
   /// ignored or type-converted, to its builtin kind.
   /// See also BuiltInPositionInfo which is a separate mechanism for a more