diff --git a/changelog b/changelog
index 5b59f4f7c0c..5f029545f1a 100644
--- a/changelog
+++ b/changelog
@@ -58,6 +58,8 @@ Version 1.11.0-svn:
      * is scaled to fit at all resolutions.
      * Removed the scrolling feature which is no longer needed.
    * Map label placement tool
+ * Engine:
+    *  Fixed bug #19599: Engine keeps redundant unit.ai_special_ information.
  * Graphics:
      * New graphics for the Spectre.
  * Language and i18n:
diff --git a/data/core/about.cfg b/data/core/about.cfg
index 0e8d7f015d9..684289bb91b 100644
--- a/data/core/about.cfg
+++ b/data/core/about.cfg
@@ -894,6 +894,9 @@
     [entry]
         name = "Andrius Štikonas"
     [/entry]
+    [entry]
+        name = "Anja Keicher (ayne)"
+    [/entry]
     [entry]
         name = "Ben Anderman (crimson_penguin)"
         comment = "unit list"
diff --git a/src/unit.cpp b/src/unit.cpp
index ac5b072f280..177eee877f2 100644
--- a/src/unit.cpp
+++ b/src/unit.cpp
@@ -156,7 +156,6 @@ unit::unit(const unit& o):
            overlays_(o.overlays_),
 
            role_(o.role_),
-           ai_special_(o.ai_special_),
            attacks_(o.attacks_),
            facing_(o.facing_),
 
@@ -236,7 +235,6 @@ unit::unit(const config &cfg, bool use_traits, game_state* state, const vconfig*
 	state_(STATE_STANDING),
 	overlays_(),
 	role_(cfg["role"]),
-	ai_special_(cfg["ai_special"]),
 	attacks_(),
 	facing_(map_location::NDIRECTIONS),
 	trait_names_(),
@@ -445,7 +443,7 @@ unit::unit(const config &cfg, bool use_traits, game_state* state, const vconfig*
 		}
 	}
 	if(cfg["ai_special"] == "guardian") {
-		set_state("guardian", true);
+		set_state(STATE_GUARDIAN, true);
 	}
 
 	// Remove animations from private cfg, they're not needed there now
@@ -597,7 +595,6 @@ unit::unit(const unit_type *t, int side, bool real_unit,
 	state_(STATE_STANDING),
 	overlays_(),
 	role_(),
-	ai_special_(),
 	attacks_(),
 	facing_(static_cast<map_location::DIRECTION>(rand()%map_location::NDIRECTIONS)),
 	trait_names_(),
@@ -1071,7 +1068,6 @@ void unit::end_turn()
 }
 void unit::new_scenario()
 {
-	ai_special_ = "";
 
 	// Set the goto-command to be going to no-where
 	goto_ = map_location();
@@ -1101,6 +1097,7 @@ void unit::new_scenario()
 	set_state(STATE_SLOWED, false);
 	set_state(STATE_POISONED, false);
 	set_state(STATE_PETRIFIED, false);
+	set_state(STATE_GUARDIAN, false);
 }
 
 void unit::heal(int amount)
@@ -1172,8 +1169,7 @@ std::map<std::string, unit::state_t> unit::get_known_boolean_state_names()
 	known_boolean_state_names_map.insert(std::make_pair("uncovered", STATE_UNCOVERED));
 	known_boolean_state_names_map.insert(std::make_pair("not_moved",STATE_NOT_MOVED));
 	known_boolean_state_names_map.insert(std::make_pair("unhealable",STATE_UNHEALABLE));
-	//not sure if "guardian" is a yes/no state.
-	//known_boolean_state_names_map.insert(std::make_pair("guardian",STATE_GUARDIAN));
+	known_boolean_state_names_map.insert(std::make_pair("guardian",STATE_GUARDIAN));
 	return known_boolean_state_names_map;
 }
 
@@ -1419,7 +1415,7 @@ bool unit::internal_matches_filter(const vconfig& cfg, const map_location& loc,
 	}
 
 	config::attribute_value cfg_ai_special = cfg["ai_special"];
-	if (!cfg_ai_special.blank() && cfg_ai_special.str() != ai_special_) {
+	if (!cfg_ai_special.blank() && ((cfg_ai_special.str() == "guardian" ? true : false)  != get_state(STATE_GUARDIAN))) {
 		return false;
 	}
 
@@ -1638,7 +1634,6 @@ void unit::write(config& cfg) const
 	cfg["variation"] = variation_;
 
 	cfg["role"] = role_;
-	cfg["ai_special"] = ai_special_;
 	cfg["flying"] = flying_;
 
 	config status_flags;
diff --git a/src/unit.hpp b/src/unit.hpp
index 5ae823bf901..e3d903c30c2 100644
--- a/src/unit.hpp
+++ b/src/unit.hpp
@@ -171,7 +171,7 @@ public:
 	bool get_state(const std::string& state) const;
 	void set_state(const std::string &state, bool value);
 	enum state_t { STATE_SLOWED = 0, STATE_POISONED, STATE_PETRIFIED,
-		STATE_UNCOVERED, STATE_NOT_MOVED, STATE_UNHEALABLE, STATE_UNKNOWN = -1 };
+		STATE_UNCOVERED, STATE_NOT_MOVED, STATE_UNHEALABLE, STATE_GUARDIAN, STATE_UNKNOWN = -1 };
 	void set_state(state_t state, bool value);
 	bool get_state(state_t state) const;
 	static state_t get_known_boolean_state_id(const std::string &state);
@@ -190,8 +190,6 @@ public:
 	void set_role(const std::string& role) { role_ = role; }
 	const std::string &get_role() const { return role_; }
 
-	void assign_ai_special(const std::string& s) { ai_special_ = s;}
-            std::string get_ai_special() const { return(ai_special_); }
 	const std::vector<attack_type>& attacks() const { return attacks_; }
 	std::vector<attack_type>& attacks() { return attacks_; }
 
@@ -436,7 +434,6 @@ private:
 	std::vector<std::string> overlays_;
 
 	std::string role_;
-	std::string ai_special_;
 	std::vector<attack_type> attacks_;
 	map_location::DIRECTION facing_;