diff --git a/src/ai/ai_config.cpp b/src/ai/ai_config.cpp
index 7493556736..55e9bc0ba1 100644
--- a/src/ai/ai_config.cpp
+++ b/src/ai/ai_config.cpp
@@ -18,6 +18,8 @@
 
 /* static */ AIConfig *AIConfig::GetConfig(CompanyID company, ScriptSettingSource source)
 {
+	assert(company < MAX_COMPANIES);
+
 	AIConfig **config;
 	if (source == SSS_FORCE_NEWGAME || (source == SSS_DEFAULT && _game_mode == GM_MENU)) {
 		config = &_settings_newgame.ai_config[company];
diff --git a/src/ai/ai_gui.cpp b/src/ai/ai_gui.cpp
index e34200460a..5a6a52cb53 100644
--- a/src/ai/ai_gui.cpp
+++ b/src/ai/ai_gui.cpp
@@ -288,7 +288,7 @@ struct AIConfigWindow : public Window {
 
 		if (!gui_scope) return;
 
-		AIConfig *config = AIConfig::GetConfig(this->selected_slot);
+		AIConfig *config = this->selected_slot == INVALID_COMPANY ? nullptr : AIConfig::GetConfig(this->selected_slot);
 
 		this->SetWidgetDisabledState(WID_AIC_DECREASE_NUMBER, GetGameSettings().difficulty.max_no_competitors == 0);
 		this->SetWidgetDisabledState(WID_AIC_INCREASE_NUMBER, GetGameSettings().difficulty.max_no_competitors == MAX_COMPANIES - 1);