diff --git a/clang/lib/StaticAnalyzer/Core/CFRefCount.cpp b/clang/lib/StaticAnalyzer/Core/CFRefCount.cpp
index 3c3bd3402ee0756644a6e6c4d35c7a33969bc692..75feba478d9390f8438b5fe95afb5865537507f0 100644
--- a/clang/lib/StaticAnalyzer/Core/CFRefCount.cpp
+++ b/clang/lib/StaticAnalyzer/Core/CFRefCount.cpp
@@ -2700,6 +2700,9 @@ public:
       return false;
     case LangOptions::GCOnly:
       return true;
+    default:
+      llvm_unreachable("Invalid/unknown GC mode.");
+      return false;
     }
   }