diff --git a/src/action/action_attack.cpp b/src/action/action_attack.cpp
index 337f904a59..cc39ae1e96 100644
--- a/src/action/action_attack.cpp
+++ b/src/action/action_attack.cpp
@@ -168,7 +168,7 @@ void COrder_Attack::Save(CFile &file, const CUnit &unit) const /* override */
 		file.printf(" \"finished\", ");
 	}
 	if (this->HasGoal()) {
-		file.printf(" \"goal\", \"%s\",", UnitReference(this->GetGoal()).c_str());
+		file.printf(" \"goal\", \"%s\",", UnitReference(*this->GetGoal()).c_str());
 	}
 	file.printf(" \"tile\", {%d, %d},", this->goalPos.x, this->goalPos.y);
 	file.printf(" \"amove-tile\", {%d, %d},", this->attackMovePos.x, this->attackMovePos.y);
diff --git a/src/action/action_board.cpp b/src/action/action_board.cpp
index fd4850343a..cfdc9d4b35 100644
--- a/src/action/action_board.cpp
+++ b/src/action/action_board.cpp
@@ -79,7 +79,7 @@ enum {
 	}
 	file.printf(" \"range\", %d,", this->Range);
 	if (this->HasGoal()) {
-		file.printf(" \"goal\", \"%s\",", UnitReference(this->GetGoal()).c_str());
+		file.printf(" \"goal\", \"%s\",", UnitReference(*this->GetGoal()).c_str());
 	}
 	file.printf(" \"state\", %d", this->State);
 
diff --git a/src/action/action_build.cpp b/src/action/action_build.cpp
index 24497193ee..c45a3fb2d8 100644
--- a/src/action/action_build.cpp
+++ b/src/action/action_build.cpp
@@ -102,7 +102,7 @@ void COrder_Build::Save(CFile &file, const CUnit &unit) const /* override */
 	file.printf(" \"tile\", {%d, %d},", this->goalPos.x, this->goalPos.y);
 
 	if (this->BuildingUnit != nullptr) {
-		file.printf(" \"building\", \"%s\",", UnitReference(this->BuildingUnit).c_str());
+		file.printf(" \"building\", \"%s\",", UnitReference(*this->BuildingUnit).c_str());
 	}
 	file.printf(" \"type\", \"%s\",", this->Type->Ident.c_str());
 	file.printf(" \"state\", %d", this->State);
diff --git a/src/action/action_built.cpp b/src/action/action_built.cpp
index da64a43a5d..b495cf7253 100644
--- a/src/action/action_built.cpp
+++ b/src/action/action_built.cpp
@@ -78,7 +78,7 @@ void COrder_Built::Save(CFile &file, const CUnit &unit) const /* override */
 		file.printf(" \"finished\", ");
 	}
 	if (this->Worker != nullptr) {
-		file.printf("\"worker\", \"%s\", ", UnitReference(this->Worker).c_str());
+		file.printf("\"worker\", \"%s\", ", UnitReference(*this->Worker).c_str());
 	}
 	const int frame = this->Frame;
 	file.printf("\"progress\", %d, \"frame\", %d", this->ProgressCounter, frame);
diff --git a/src/action/action_defend.cpp b/src/action/action_defend.cpp
index bb3d6532c7..c0625f6316 100644
--- a/src/action/action_defend.cpp
+++ b/src/action/action_defend.cpp
@@ -79,7 +79,7 @@ void COrder_Defend::Save(CFile &file, const CUnit &unit) const /* override */
 	}
 	file.printf(" \"range\", %d,", this->Range);
 	if (this->HasGoal()) {
-		file.printf(" \"goal\", \"%s\",", UnitReference(this->GetGoal()).c_str());
+		file.printf(" \"goal\", \"%s\",", UnitReference(*this->GetGoal()).c_str());
 	}
 	file.printf(" \"tile\", {%d, %d},", this->goalPos.x, this->goalPos.y);
 
diff --git a/src/action/action_follow.cpp b/src/action/action_follow.cpp
index a02d6cdcda..3f22c7060e 100644
--- a/src/action/action_follow.cpp
+++ b/src/action/action_follow.cpp
@@ -87,7 +87,7 @@ void COrder_Follow::Save(CFile &file, const CUnit &unit) const /* override */
 	}
 	file.printf(" \"range\", %d,", this->Range);
 	if (this->HasGoal()) {
-		file.printf(" \"goal\", \"%s\",", UnitReference(this->GetGoal()).c_str());
+		file.printf(" \"goal\", \"%s\",", UnitReference(*this->GetGoal()).c_str());
 	}
 	file.printf(" \"tile\", {%d, %d},", this->goalPos.x, this->goalPos.y);
 
diff --git a/src/action/action_repair.cpp b/src/action/action_repair.cpp
index 64828f45ea..92a1b3bb08 100644
--- a/src/action/action_repair.cpp
+++ b/src/action/action_repair.cpp
@@ -86,12 +86,12 @@ void COrder_Repair::Save(CFile &file, const CUnit &unit) const /* override */
 		file.printf(" \"finished\", ");
 	}
 	if (this->HasGoal()) {
-		file.printf(" \"goal\", \"%s\",", UnitReference(this->GetGoal()).c_str());
+		file.printf(" \"goal\", \"%s\",", UnitReference(*this->GetGoal()).c_str());
 	}
 	file.printf(" \"tile\", {%d, %d},", this->goalPos.x, this->goalPos.y);
 
 	if (this->ReparableTarget != nullptr) {
-		file.printf(" \"repair-target\", \"%s\",", UnitReference(this->GetReparableTarget()).c_str());
+		file.printf(" \"repair-target\", \"%s\",", UnitReference(*this->GetReparableTarget()).c_str());
 	}
 
 	file.printf(" \"repaircycle\", %d,", this->RepairCycle);
diff --git a/src/action/action_resource.cpp b/src/action/action_resource.cpp
index 8b3ef870f3..7783154deb 100644
--- a/src/action/action_resource.cpp
+++ b/src/action/action_resource.cpp
@@ -251,20 +251,20 @@ void COrder_Resource::Save(CFile &file, const CUnit &unit) const /* override */
 		file.printf(" \"finished\",");
 	}
 	if (this->HasGoal()) {
-		file.printf(" \"goal\", \"%s\",", UnitReference(this->GetGoal()).c_str());
+		file.printf(" \"goal\", \"%s\",", UnitReference(*this->GetGoal()).c_str());
 	}
 	file.printf(" \"tile\", {%d, %d},", this->goalPos.x, this->goalPos.y);
 
 	Assert(this->worker != nullptr && worker->IsAlive());
-	file.printf(" \"worker\", \"%s\",", UnitReference(worker).c_str());
+	file.printf(" \"worker\", \"%s\",", UnitReference(*worker).c_str());
 	file.printf(" \"current-res\", %d,", this->CurrentResource);
 
 	file.printf(" \"res-pos\", {%d, %d},", this->Resource.Pos.x, this->Resource.Pos.y);
 	if (this->Resource.Mine != nullptr) {
-		file.printf(" \"res-mine\", \"%s\",", UnitReference(this->Resource.Mine).c_str());
+		file.printf(" \"res-mine\", \"%s\",", UnitReference(*this->Resource.Mine).c_str());
 	}
 	if (this->Depot != nullptr) {
-		file.printf(" \"res-depot\", \"%s\",", UnitReference(this->Depot).c_str());
+		file.printf(" \"res-depot\", \"%s\",", UnitReference(*this->Depot).c_str());
 	}
 	if (this->DoneHarvesting) {
 		file.printf(" \"done-harvesting\",");
diff --git a/src/action/action_spellcast.cpp b/src/action/action_spellcast.cpp
index a49941aa56..5eedd12f3c 100644
--- a/src/action/action_spellcast.cpp
+++ b/src/action/action_spellcast.cpp
@@ -96,7 +96,7 @@ void COrder_SpellCast::Save(CFile &file, const CUnit &unit) const /* override */
 	}
 	file.printf(" \"range\", %d,", this->Range);
 	if (this->HasGoal()) {
-		file.printf(" \"goal\", \"%s\",", UnitReference(this->GetGoal()).c_str());
+		file.printf(" \"goal\", \"%s\",", UnitReference(*this->GetGoal()).c_str());
 	}
 	file.printf(" \"tile\", {%d, %d},", this->goalPos.x, this->goalPos.y);
 
diff --git a/src/action/action_unload.cpp b/src/action/action_unload.cpp
index d714f437d1..5c51df8935 100644
--- a/src/action/action_unload.cpp
+++ b/src/action/action_unload.cpp
@@ -81,7 +81,7 @@ void COrder_Unload::Save(CFile &file, const CUnit &unit) const /* override */
 	}
 	file.printf(" \"retries\", %d,", this->Retries);
 	if (this->HasGoal()) {
-		file.printf(" \"goal\", \"%s\",", UnitReference(this->GetGoal()).c_str());
+		file.printf(" \"goal\", \"%s\",", UnitReference(*this->GetGoal()).c_str());
 	}
 	file.printf(" \"tile\", {%d, %d}, ", this->goalPos.x, this->goalPos.y);
 	file.printf("\"state\", %d", this->State);
diff --git a/src/include/unit.h b/src/include/unit.h
index 23af8a7813..f9f6d52f64 100644
--- a/src/include/unit.h
+++ b/src/include/unit.h
@@ -652,8 +652,6 @@ extern bool CanTransport(const CUnit &transporter, const CUnit &unit);
 
 /// Generate a unit reference, a printable unique string for unit
 extern std::string UnitReference(const CUnit &unit);
-/// Generate a unit reference, a printable unique string for unit
-extern std::string UnitReference(const CUnitPtr &unit);
 
 /// save unit-structure
 extern void SaveUnit(const CUnit &unit, CFile &file);
diff --git a/src/include/unitptr.h b/src/include/unitptr.h
index e3a31746cd..87323c1144 100644
--- a/src/include/unitptr.h
+++ b/src/include/unitptr.h
@@ -42,7 +42,8 @@ class CUnitPtr
 {
 public:
 	CUnitPtr() : unit(nullptr) {}
-	CUnitPtr(CUnit *u);
+	CUnitPtr(std::nullptr_t) : unit(nullptr) {}
+	explicit CUnitPtr(CUnit *u);
 	CUnitPtr(const CUnitPtr &u);
 	~CUnitPtr() { Reset(); }
 
diff --git a/src/missile/missile.cpp b/src/missile/missile.cpp
index 07ff518621..3b643c2db7 100644
--- a/src/missile/missile.cpp
+++ b/src/missile/missile.cpp
@@ -1212,10 +1212,10 @@ void Missile::SaveMissile(CFile &file) const
 	file.printf(",\n  \"frame\", %d, \"state\", %d, \"anim-wait\", %d, \"wait\", %d, \"delay\", %d,\n ",
 				this->SpriteFrame, this->State, this->AnimWait, this->Wait, this->Delay);
 	if (this->SourceUnit != nullptr) {
-		file.printf(" \"source\", \"%s\",", UnitReference(this->SourceUnit).c_str());
+		file.printf(" \"source\", \"%s\",", UnitReference(*this->SourceUnit).c_str());
 	}
 	if (this->TargetUnit != nullptr) {
-		file.printf(" \"target\", \"%s\",", UnitReference(this->TargetUnit).c_str());
+		file.printf(" \"target\", \"%s\",", UnitReference(*this->TargetUnit).c_str());
 	}
 	file.printf(" \"damage\", %d,", this->Damage);
 	file.printf(" \"ttl\", %d,", this->TTL);
diff --git a/src/unit/unit_save.cpp b/src/unit/unit_save.cpp
index 5b10415abf..ae0a09ff77 100644
--- a/src/unit/unit_save.cpp
+++ b/src/unit/unit_save.cpp
@@ -66,15 +66,6 @@ std::string UnitReference(const CUnit &unit)
 	return ss.str();
 }
 
-/**
-**  Generate a unit reference, a printable unique string for unit.
-*/
-std::string UnitReference(const CUnitPtr &unit)
-{
-	Assert(unit != nullptr);
-	return UnitReference(*unit);
-}
-
 void PathFinderInput::Save(CFile &file) const
 {
 	file.printf("\"pathfinder-input\", {");