diff --git a/lib/Driver/ToolChain.cpp b/lib/Driver/ToolChain.cpp
index 59932f611e..b24de5d132 100644
--- a/lib/Driver/ToolChain.cpp
+++ b/lib/Driver/ToolChain.cpp
@@ -113,6 +113,8 @@ Tool *ToolChain::getTool(Action::ActionClass AC) const {
   case Action::MigrateJobClass:
     return getClang();
   }
+
+  llvm_unreachable("Invalid tool kind.");
 }
 
 Tool &ToolChain::SelectTool(const JobAction &JA) const {