diff --git a/src/gui.h b/src/gui.h
--- a/src/gui.h
+++ b/src/gui.h
@@ -49,7 +49,7 @@ void ShowIndustryDirectory();
 void ShowIndustryCargoesWindow();
 void ShowSubsidiesList();
 void ShowGoalsList(CompanyID company);
-void ShowGoalQuestion(uint16 id, byte type, uint32 button_mask, const char *question);
+void ShowGoalQuestion(uint16 id, byte type, uint32 button_mask, const std::string &question);
 void ShowStoryBook(CompanyID company, uint16 page_id = INVALID_STORY_PAGE);
 
 void ShowEstimatedCostOrIncome(Money cost, int x, int y);