diff --git a/clangd/FindTarget.cpp b/clangd/FindTarget.cpp
index 170f8f6..ea7f332 100644
--- a/clangd/FindTarget.cpp
+++ b/clangd/FindTarget.cpp
@@ -365,6 +365,7 @@
     REL_CASE(TemplatePattern);
 #undef REL_CASE
   };
+  llvm_unreachable("Unhandled DeclRelation enum");
 }
 llvm::raw_ostream &operator<<(llvm::raw_ostream &OS, DeclRelationSet RS) {
   const char *Sep = "";