diff --git a/runtime/debugger.cc b/runtime/debugger.cc
index 96b44bf..c53f6b2 100644
--- a/runtime/debugger.cc
+++ b/runtime/debugger.cc
@@ -3504,6 +3504,7 @@
   switch (tag) {
     default:
       LOG(FATAL) << "unknown JDWP tag: " << PrintableChar(tag);
+      UNREACHABLE();
 
     // Primitives.
     case JDWP::JT_BYTE:    return 'B';