diff --git a/src/unit.cpp b/src/unit.cpp
index 1db5236575c..8527a404c67 100644
--- a/src/unit.cpp
+++ b/src/unit.cpp
@@ -1803,7 +1803,7 @@ const surface unit::still_image(bool scaled) const
 	return unit_image;
 }
 
-void unit::set_standing(bool with_bars)
+void unit::set_standing(bool with_bars) const
 {
 	display *disp = display::get_singleton();
 	if (preferences::show_standing_animations()&& !incapacitated()) {
@@ -1815,28 +1815,28 @@ void unit::set_standing(bool with_bars)
 	}
 }
 
-void unit::set_ghosted(bool with_bars)
+void unit::set_ghosted(bool with_bars) const
 {
 	display *disp = display::get_singleton();
 	start_animation(INT_MAX, choose_animation(*disp, loc_, "ghosted"),
 			with_bars);
 }
 
-void unit::set_disabled_ghosted(bool with_bars)
+void unit::set_disabled_ghosted(bool with_bars) const
 {
 	display *disp = display::get_singleton();
 	start_animation(INT_MAX, choose_animation(*disp, loc_, "disabled_ghosted"),
 			with_bars);
 }
 
-void unit::set_idling()
+void unit::set_idling() const
 {
 	display *disp = display::get_singleton();
 	start_animation(INT_MAX, choose_animation(*disp, loc_, "idling"),
 		true, "", 0, STATE_FORGET);
 }
 
-void unit::set_selecting()
+void unit::set_selecting() const
 {
 	const display *disp =  display::get_singleton();
 	if (preferences::show_standing_animations() && !get_state(STATE_PETRIFIED)) {
@@ -1848,8 +1848,8 @@ void unit::set_selecting()
 	}
 }
 
-void unit::start_animation(int start_time, const unit_animation *animation,
-	bool with_bars,  const std::string &text, Uint32 text_color, STATE state)
+void unit::start_animation (int start_time, const unit_animation *animation,
+	bool with_bars,  const std::string &text, Uint32 text_color, STATE state) const
 {
 	const display * disp =  display::get_singleton();
 	if (!animation) {
@@ -1884,7 +1884,7 @@ void unit::set_facing(map_location::DIRECTION dir) {
 	// Else look at yourself (not available so continue to face the same direction)
 }
 
-void unit::redraw_unit()
+void unit::redraw_unit () const
 {
 	display &disp = *display::get_singleton();
 	const gamemap &map = disp.get_map();
@@ -2151,7 +2151,7 @@ void unit::redraw_unit()
 	refreshing_ = false;
 }
 
-void unit::clear_haloes()
+void unit::clear_haloes () const
 {
 	if(unit_halo_ != halo::NO_HALO) {
 		halo::remove(unit_halo_);
@@ -2159,7 +2159,7 @@ void unit::clear_haloes()
 	}
 	if(anim_ ) anim_->clear_haloes();
 }
-bool unit::invalidate(const display & disp)
+bool unit::invalidate (const display & disp) const
 {
 	bool result = false;
 
@@ -3026,7 +3026,7 @@ int side_upkeep(int side)
 	return res;
 }
 
-void unit::refresh()
+void unit::refresh() const
 {
 	if (state_ == STATE_FORGET && anim_ && anim_->animation_finished_potential())
 	{
diff --git a/src/unit.hpp b/src/unit.hpp
index 0cba520ba23..02d323c06b4 100644
--- a/src/unit.hpp
+++ b/src/unit.hpp
@@ -204,7 +204,7 @@ public:
 	void end_turn();
 	void new_scenario();
 	/** Called on every draw */
-	void refresh();
+	void refresh() const;
 
 	bool take_hit(int damage) { hit_points_ -= damage; return hit_points_ <= 0; }
 	void heal(int amount);
@@ -249,23 +249,22 @@ public:
 	const surface still_image(bool scaled = false) const;
 
 	/** draw a unit.  */
-	void redraw_unit();
+	void redraw_unit() const;
 	/** Clear unit_halo_  */
-	void clear_haloes();
+	void clear_haloes() const;
 
-	void set_standing(bool with_bars = true);
+	void set_standing(bool with_bars = true) const;
 
-	void set_ghosted(bool with_bars = true);
-	void set_disabled_ghosted(bool with_bars = true);
+	void set_ghosted(bool with_bars = true) const;
+	void set_disabled_ghosted(bool with_bars = true) const;
 
-	void set_idling();
-	void set_selecting();
-	unit_animation* get_animation() {  return anim_.get();}
-	const unit_animation* get_animation() const {  return anim_.get();}
+	void set_idling() const;
+	void set_selecting() const;
+	unit_animation* get_animation() const {  return anim_.get();}
 	void set_facing(map_location::DIRECTION dir);
 	map_location::DIRECTION facing() const { return facing_; }
 
-	bool invalidate(const display & disp);
+	bool invalidate(const display & disp) const;
 	const std::vector<t_string>& trait_names() const { return trait_names_; }
 	const std::vector<t_string>& trait_descriptions() const { return trait_descriptions_; }
 	std::vector<std::string> get_traits_list() const;
@@ -327,9 +326,9 @@ public:
 		STATE_STANDING,   /** anim must fit in a hex */
 		STATE_FORGET,     /** animation will be automatically replaced by a standing anim when finished */
 		STATE_ANIM};      /** normal anims */
-	void start_animation(int start_time, const unit_animation *animation,
+	void start_animation (int start_time, const unit_animation *animation,
 		bool with_bars,  const std::string &text = "",
-		Uint32 text_color = 0, STATE state = STATE_ANIM);
+		Uint32 text_color = 0, STATE state = STATE_ANIM) const;
 
 	/** The name of the file to game_display (used in menus). */
 	std::string absolute_image() const;
@@ -488,7 +487,8 @@ private:
 	config events_;
 	config filter_recall_;
 	bool emit_zoc_;
-	STATE state_;
+
+	mutable STATE state_; //animation state
 
 	std::vector<std::string> overlays_;
 
@@ -508,16 +508,16 @@ private:
 	// Animations:
 	std::vector<unit_animation> animations_;
 
-	boost::scoped_ptr<unit_animation> anim_;
-	int next_idling_;
-	int frame_begin_time_;
+	mutable boost::scoped_ptr<unit_animation> anim_;
+	mutable int next_idling_;      // used for animation
+	mutable int frame_begin_time_; // used for animation
 
 
-	int unit_halo_;
+	mutable int unit_halo_; // flag used for drawing / animation
 	bool getsHit_;
-	bool refreshing_; // avoid infinite recursion
+	mutable bool refreshing_; // avoid infinite recursion. flag used for drawing / animation
 	bool hidden_;
-	bool draw_bars_;
+	mutable bool draw_bars_; // flag used for drawing / animation
 	double hp_bar_scaling_, xp_bar_scaling_;
 
 	config modifications_;