diff --git a/src/formula/callable_objects.cpp b/src/formula/callable_objects.cpp
index 83d9bbe3f574..248f22038ab1 100644
--- a/src/formula/callable_objects.cpp
+++ b/src/formula/callable_objects.cpp
@@ -528,7 +528,7 @@ void config_callable::get_inputs(std::vector<game_logic::formula_input>* inputs)
 int config_callable::do_compare(const game_logic::formula_callable* callable) const
 {
 	const config_callable* cfg_callable = dynamic_cast<const config_callable*>(callable);
-	if(cfg_callable == NULL) {
+	if(cfg_callable == nullptr) {
 		return formula_callable::do_compare(callable);
 	}
 	
diff --git a/src/scripting/lua_formula_bridge.cpp b/src/scripting/lua_formula_bridge.cpp
index 477570399132..409cd9961210 100644
--- a/src/scripting/lua_formula_bridge.cpp
+++ b/src/scripting/lua_formula_bridge.cpp
@@ -77,7 +77,7 @@ class lua_callable : public formula_callable {
 	}
 	int do_compare(const formula_callable* other) const {
 		const lua_callable* lua = dynamic_cast<const lua_callable*>(other);
-		if(lua == NULL) {
+		if(lua == nullptr) {
 			return formula_callable::do_compare(other);
 		}
 		if(mState == lua->mState) { // Which should always be the case, but let's be safe here
diff --git a/src/scripting/lua_formula_bridge.hpp b/src/scripting/lua_formula_bridge.hpp
index f64b7f434b38..7fb4774dd986 100644
--- a/src/scripting/lua_formula_bridge.hpp
+++ b/src/scripting/lua_formula_bridge.hpp
@@ -36,9 +36,9 @@ namespace lua_formula_bridge {
 	class fwrapper {
 		boost::shared_ptr<game_logic::formula> formula_ptr;
 	public:
-		fwrapper(const std::string& code, game_logic::function_symbol_table* functions = NULL);
+		fwrapper(const std::string& code, game_logic::function_symbol_table* functions = nullptr);
 		std::string str() const;
-		variant evaluate(const game_logic::formula_callable& variables, game_logic::formula_debugger* fdb = NULL) const;
+		variant evaluate(const game_logic::formula_callable& variables, game_logic::formula_debugger* fdb = nullptr) const;
 	};
 	
 } // end namespace lua_formula_bridge