diff --git a/clang/tools/include-mapping/cppreference_parser.py b/clang/tools/include-mapping/cppreference_parser.py
--- a/clang/tools/include-mapping/cppreference_parser.py
+++ b/clang/tools/include-mapping/cppreference_parser.py
@@ -142,7 +142,8 @@
       if variant and variant not in variants_for_symbol:
         continue
       path = os.path.join(root_dir, symbol_page_path)
-      results.append((symbol_name,
+      if os.path.isfile(path):
+        results.append((symbol_name,
                       pool.apply_async(_ReadSymbolPage, (path, symbol_name))))
 
     # Build map from symbol name to a set of headers.