diff --git a/clang-tools-extra/clangd/CodeComplete.cpp b/clang-tools-extra/clangd/CodeComplete.cpp
index 2eeaf54ea1ce..db8069bb7487 100644
--- a/clang-tools-extra/clangd/CodeComplete.cpp
+++ b/clang-tools-extra/clangd/CodeComplete.cpp
@@ -828,6 +828,7 @@ bool allowIndex(CodeCompletionContext &CC) {
   case NestedNameSpecifier::Identifier:
     return false;
   }
+  llvm_unreachable("invalid NestedNameSpecifier kind");
 }
 
 } // namespace