diff --git a/runtime/runtime_callbacks.h b/runtime/runtime_callbacks.h
index 6344c69..e580e78 100644
--- a/runtime/runtime_callbacks.h
+++ b/runtime/runtime_callbacks.h
@@ -58,9 +58,10 @@
 class RuntimePhaseCallback {
  public:
   enum RuntimePhase {
-    kStart,  // The runtime is started.
-    kInit,   // The runtime is initialized (and will run user code soon).
-    kDeath,  // The runtime just died.
+    kInitialAgents,   // Initial agent loading is done.
+    kStart,           // The runtime is started.
+    kInit,            // The runtime is initialized (and will run user code soon).
+    kDeath,           // The runtime just died.
   };
 
   virtual ~RuntimePhaseCallback() {}