diff --git a/CCallback.cpp b/CCallback.cpp
index 8009bc7db..da280db1c 100644
--- a/CCallback.cpp
+++ b/CCallback.cpp
@@ -80,7 +80,7 @@ void CCallback::recruitCreatures(const CGDwelling *obj, const CArmedInstance * d
 
 bool CCallback::dismissCreature(const CArmedInstance *obj, SlotID stackPos)
 {
-	if(((player>=0)  &&  obj->tempOwner != player) || (obj->stacksCount()<2  && obj->needsLastStack()))
+	if((player && obj->tempOwner != player) || (obj->stacksCount()<2  && obj->needsLastStack()))
 		return false;
 
 	DisbandCreature pack(stackPos,obj->id);
diff --git a/lib/CArtHandler.cpp b/lib/CArtHandler.cpp
index 2d9dd0172..0026a6672 100644
--- a/lib/CArtHandler.cpp
+++ b/lib/CArtHandler.cpp
@@ -671,7 +671,7 @@ boost::optional<std::vector<CArtifact*>&> CArtHandler::listFromClass( CArtifact:
 	case CArtifact::ART_RELIC:
 		return relics;
 	default: //special artifacts should not be erased
-		return nullptr;
+		return boost::optional<std::vector<CArtifact*>&>();
 	}
 }
 
diff --git a/lib/CGameInfoCallback.cpp b/lib/CGameInfoCallback.cpp
index 051bb9cb9..2a59b96d3 100644
--- a/lib/CGameInfoCallback.cpp
+++ b/lib/CGameInfoCallback.cpp
@@ -403,7 +403,7 @@ std::vector <const CGObjectInstance * > CGameInfoCallback::getVisitableObjs(int3
 
 	for(const CGObjectInstance * obj : t->visitableObjects)
 	{
-		if(player < nullptr || obj->ID != Obj::EVENT) //hide events from players
+		if(player || obj->ID != Obj::EVENT) //hide events from players
 			ret.push_back(obj);
 	}