diff --git a/clang/include/clang/Basic/Linkage.h b/clang/include/clang/Basic/Linkage.h
index 9cf36e522947f..fcf56b93b9781 100644
--- a/clang/include/clang/Basic/Linkage.h
+++ b/clang/include/clang/Basic/Linkage.h
@@ -100,6 +100,7 @@ inline bool isExternallyVisible(Linkage L) {
   case Linkage::External:
     return true;
   }
+  llvm_unreachable("Unhandled Linkage enum");
 }
 
 inline Linkage getFormalLinkage(Linkage L) {
diff --git a/clang/lib/AST/Decl.cpp b/clang/lib/AST/Decl.cpp
index e8062b680fbc3..42ba8582c46de 100644
--- a/clang/lib/AST/Decl.cpp
+++ b/clang/lib/AST/Decl.cpp
@@ -1934,6 +1934,7 @@ bool NamedDecl::hasLinkage() const {
   case Linkage::External:
     return true;
   }
+  llvm_unreachable("Unhandled Linkage enum");
 }
 
 NamedDecl *NamedDecl::getUnderlyingDeclImpl() {