diff --git a/common/main/ai.h b/common/main/ai.h
index 7b93078f5..85c416838 100644
--- a/common/main/ai.h
+++ b/common/main/ai.h
@@ -239,17 +239,6 @@ extern fix64            Boss_hit_time;
 // These globals are set by a call to find_vector_intersection, which is a slow routine,
 // so we don't want to call it again (for this object) unless we have to.
 
-#ifndef NDEBUG
-// Index into this array with ailp->mode
-
-// Index into this array with aip->behavior
-
-// Index into this array with aip->GOAL_STATE or aip->CURRENT_STATE
-
-extern int Do_ai_flag;
-
-#endif //ifndef NDEBUG
-
 extern int Stolen_item_index;   // Used in ai.c for controlling rate of Thief flare firing.
 
 // -- unused, 08/07/95 -- extern void ai_turn_randomly(vms_vector *vec_to_player, object *obj, fix rate, int previous_visibility);
diff --git a/similar/main/ai.cpp b/similar/main/ai.cpp
index 247e78f9a..609df4887 100644
--- a/similar/main/ai.cpp
+++ b/similar/main/ai.cpp
@@ -1603,10 +1603,6 @@ void do_ai_robot_hit(const vobjptridx_t objp, player_awareness_type_t type)
 	}
 
 }
-#ifndef NDEBUG
-int	Do_ai_flag=1;
-#endif
-
 #define	CHASE_TIME_LENGTH		(F1_0*8)
 #define	DEFAULT_ROBOT_SOUND_VOLUME		F1_0
 int		Robot_sound_volume=DEFAULT_ROBOT_SOUND_VOLUME;
@@ -2973,9 +2969,6 @@ void do_ai_frame(const vobjptridx_t obj)
 	if ((aip->behavior == ai_behavior::AIB_RUN_FROM) && (ailp->mode != ai_mode::AIM_RUN_FROM_OBJECT))
 		Int3(); // This is peculiar.  Behavior is run from, but mode is not.  Contact Mike.
 
-	if (!Do_ai_flag)
-		return;
-
 	if (Break_on_object != object_none)
 		if ((obj) == Break_on_object)
 			Int3(); // Contact Mike: This is a debug break