3 files changed, 22 insertions, 2 deletions
diff --git a/src/ai/ai_instance.cpp b/src/ai/ai_instance.cpp
index a5ef5135b..6e1ffa0c1 100644
--- a/src/ai/ai_instance.cpp
+++ b/src/ai/ai_instance.cpp
@@ -353,6 +353,7 @@ void AIInstance::GameLoop()
 			this->suspend  = e.GetSuspendTime();
 			this->callback = e.GetSuspendCallback();
 		} catch (AI_FatalError e) {
+			this->is_dead = true;
 			this->engine->ThrowError(e.GetErrorMessage());
 			this->engine->ResumeError();
 			this->Died();
@@ -373,6 +374,7 @@ void AIInstance::GameLoop()
 		this->suspend  = e.GetSuspendTime();
 		this->callback = e.GetSuspendCallback();
 	} catch (AI_FatalError e) {
+		this->is_dead = true;
 		this->engine->ThrowError(e.GetErrorMessage());
 		this->engine->ResumeError();
 		this->Died();
diff --git a/src/ai/api/ai_execmode.cpp b/src/ai/api/ai_execmode.cpp
index 941718bee..b51adfd48 100644
--- a/src/ai/api/ai_execmode.cpp
+++ b/src/ai/api/ai_execmode.cpp
@@ -4,6 +4,9 @@
 
 #include "ai_execmode.hpp"
 #include "../../command_type.h"
+#include "../../company_base.h"
+#include "../../company_func.h"
+#include "../ai_instance.hpp"
 
 bool AIExecMode::ModeProc(TileIndex tile, uint32 p1, uint32 p2, uint procc, CommandCost costs)
 {
@@ -21,6 +24,12 @@ AIExecMode::AIExecMode()
 
 AIExecMode::~AIExecMode()
 {
-	assert(this->GetDoCommandModeInstance() == this);
+	if (this->GetDoCommandModeInstance() != this) {
+		AIInstance *instance = Company::Get(_current_company)->ai_instance;
+		/* Ignore this error if the AI already died. */
+		if (!instance->IsDead()) {
+			throw AI_FatalError("AIExecMode object was removed while it was not the latest AI*Mode object created.");
+		}
+	}
 	this->SetDoCommandMode(this->last_mode, this->last_instance);
 }
diff --git a/src/ai/api/ai_testmode.cpp b/src/ai/api/ai_testmode.cpp
index 484333b42..114366722 100644
--- a/src/ai/api/ai_testmode.cpp
+++ b/src/ai/api/ai_testmode.cpp
@@ -4,6 +4,9 @@
 
 #include "ai_testmode.hpp"
 #include "../../command_type.h"
+#include "../../company_base.h"
+#include "../../company_func.h"
+#include "../ai_instance.hpp"
 
 bool AITestMode::ModeProc(TileIndex tile, uint32 p1, uint32 p2, uint procc, CommandCost costs)
 {
@@ -21,6 +24,12 @@ AITestMode::AITestMode()
 
 AITestMode::~AITestMode()
 {
-	assert(this->GetDoCommandModeInstance() == this);
+	if (this->GetDoCommandModeInstance() != this) {
+		AIInstance *instance = Company::Get(_current_company)->ai_instance;
+		/* Ignore this error if the AI already died. */
+		if (!instance->IsDead()) {
+			throw AI_FatalError("AITestmode object was removed while it was not the latest AI*Mode object created.");
+		}
+	}
 	this->SetDoCommandMode(this->last_mode, this->last_instance);
 }