diff --git a/clang-tools-extra/clangd/index/SymbolID.h b/clang-tools-extra/clangd/index/SymbolID.h
--- a/clang-tools-extra/clangd/index/SymbolID.h
+++ b/clang-tools-extra/clangd/index/SymbolID.h
@@ -15,6 +15,7 @@
 #include "llvm/Support/Error.h"
 #include "llvm/Support/raw_ostream.h"
 #include <array>
+#include <cstdint>
 #include <string>
 
 namespace clang {
@@ -53,8 +54,10 @@
   std::string str() const;
   static llvm::Expected<SymbolID> fromStr(llvm::StringRef);
 
+  bool isValid() const { return HashValue != std::array<uint8_t, RawSize>{}; }
+
 private:
-  std::array<uint8_t, RawSize> HashValue;
+  std::array<uint8_t, RawSize> HashValue{};
 };
 
 llvm::hash_code hash_value(const SymbolID &ID);