diff --git a/indra/aistatemachine/aistatemachine.cpp b/indra/aistatemachine/aistatemachine.cpp
index 642be5d2f..cec58baec 100644
--- a/indra/aistatemachine/aistatemachine.cpp
+++ b/indra/aistatemachine/aistatemachine.cpp
@@ -1173,6 +1173,16 @@ void AIStateMachine::yield(AIEngine* engine)
   mYieldEngine = engine;
 }
 
+bool AIStateMachine::yield_if_not(AIEngine* engine)
+{
+  if (engine && multiplex_state_type_rat(mState)->current_engine != engine)
+  {
+	yield(engine);
+	return true;
+  }
+  return false;
+}
+
 void AIStateMachine::yield_frame(unsigned int frames)
 {
   DoutEntering(dc::statemachine(mSMDebug), "AIStateMachine::yield_frame(" << frames << ") [" << (void*)this << "]");
diff --git a/indra/aistatemachine/aistatemachine.h b/indra/aistatemachine/aistatemachine.h
index 0086c03a7..2e5a47acc 100644
--- a/indra/aistatemachine/aistatemachine.h
+++ b/indra/aistatemachine/aistatemachine.h
@@ -237,6 +237,7 @@ class AIStateMachine : public LLThreadSafeRefCount
 	void yield(AIEngine* engine);											// Yield to give CPU to other state machines, but do not go idle. Continue running from engine 'engine'.
 	void yield_frame(unsigned int frames);									// Run from the main-thread engine after at least 'frames' frames have passed.
 	void yield_ms(unsigned int ms);											// Run from the main-thread engine after roughly 'ms' miliseconds have passed.
+	bool yield_if_not(AIEngine* engine);									// Do not really yield, unless the current engine is not 'engine'. Returns true if it switched engine.
 
   public:
 	// This function can be called from multiplex_imp(), but also by a child state machine and