diff --git a/src/openrct2/interface/Viewport.cpp b/src/openrct2/interface/Viewport.cpp
index a083fa62db..d1ca5556ac 100644
--- a/src/openrct2/interface/Viewport.cpp
+++ b/src/openrct2/interface/Viewport.cpp
@@ -700,7 +700,7 @@ void viewport_update_smart_sprite_follow(rct_window* window)
     }
 }
 
-viewport_focus viewport_update_smart_guest_follow(rct_window* window, Peep* peep)
+viewport_focus viewport_update_smart_guest_follow(rct_window* window, const Peep* peep)
 {
     viewport_focus focus{};
     focus.type = VIEWPORT_FOCUS_TYPE_SPRITE;
@@ -759,7 +759,7 @@ viewport_focus viewport_update_smart_guest_follow(rct_window* window, Peep* peep
     return focus;
 }
 
-void viewport_update_smart_staff_follow(rct_window* window, Peep* peep)
+void viewport_update_smart_staff_follow(rct_window* window, const Peep* peep)
 {
     sprite_focus focus = {};
 
diff --git a/src/openrct2/interface/Viewport.h b/src/openrct2/interface/Viewport.h
index 3bd4f8880a..4c72fed796 100644
--- a/src/openrct2/interface/Viewport.h
+++ b/src/openrct2/interface/Viewport.h
@@ -111,8 +111,8 @@ void viewports_invalidate(int32_t left, int32_t top, int32_t right, int32_t bott
 void viewport_update_position(rct_window* window);
 void viewport_update_sprite_follow(rct_window* window);
 void viewport_update_smart_sprite_follow(rct_window* window);
-viewport_focus viewport_update_smart_guest_follow(rct_window* window, Peep* peep);
-void viewport_update_smart_staff_follow(rct_window* window, Peep* peep);
+viewport_focus viewport_update_smart_guest_follow(rct_window* window, const Peep* peep);
+void viewport_update_smart_staff_follow(rct_window* window, const Peep* peep);
 void viewport_update_smart_vehicle_follow(rct_window* window);
 void viewport_render(
     rct_drawpixelinfo* dpi, const rct_viewport* viewport, int32_t left, int32_t top, int32_t right, int32_t bottom,