diff --git a/clang/include/clang/AST/RecursiveASTVisitor.h b/clang/include/clang/AST/RecursiveASTVisitor.h
index 79e5294a3ca179..ae6442d75dd4b4 100644
--- a/clang/include/clang/AST/RecursiveASTVisitor.h
+++ b/clang/include/clang/AST/RecursiveASTVisitor.h
@@ -551,6 +551,7 @@ bool RecursiveASTVisitor<Derived>::TraverseConceptRequirement(
     return getDerived().TraverseConceptNestedRequirement(
         cast<concepts::NestedRequirement>(R));
   }
+  llvm_unreachable("unexpected case");
 }
 
 template <typename Derived>