diff --git a/McZapkie/Mover.cpp b/McZapkie/Mover.cpp
index 330e8eb8..34caced1 100644
--- a/McZapkie/Mover.cpp
+++ b/McZapkie/Mover.cpp
@@ -809,6 +809,19 @@ bool TMoverParameters::ChangeCab(int direction)
 // rozruch wysoki (true) albo niski (false)
 bool TMoverParameters::CurrentSwitch(bool const State)
 {
+	// TBD, TODO: split off shunt mode toggle into a separate command? It doesn't make much sense to have these two together like that
+	// the diesels with a shunt mode have no motor overload relay threshold to switch, the switch sets their shunt mode alone.
+	// MaxCurrentSwitch() takes any change of the setting, so asked first it took the first move of the switch (eu07/maszyna#497)
+	if (true == ShuntModeAllow && (EngineType == TEngineType::DieselEngine || EngineType == TEngineType::DieselElectric))
+	{
+		// dla 2Ls150 przed ustawieniem kierunku, for SM42/SP42 at the controller's zero position
+		if (EngineType == TEngineType::DieselEngine ? DirActive != 0 : false == IsMainCtrlNoPowerPos())
+		{
+			return false;
+		}
+		ShuntMode = State;
+		return true;
+	}
 
 	if (MaxCurrentSwitch(State))
 	{
@@ -818,20 +831,6 @@ bool TMoverParameters::CurrentSwitch(bool const State)
 		}
 		return true;
 	}
-	// TBD, TODO: split off shunt mode toggle into a separate command? It doesn't make much sense to have these two together like that
-	// dla 2Ls150
-	if (EngineType == TEngineType::DieselEngine && true == ShuntModeAllow && DirActive == 0)
-	{
-		// przed ustawieniem kierunku
-		ShuntMode = State;
-		return true;
-	}
-	// for SM42/SP42
-	if (EngineType == TEngineType::DieselElectric && true == ShuntModeAllow && IsMainCtrlNoPowerPos())
-	{
-		ShuntMode = State;
-		return true;
-	}
 
 	return false;
 };
diff --git a/tests/unit/test_diesel.cpp b/tests/unit/test_diesel.cpp
index 07686dc1..c4ea147d 100644
--- a/tests/unit/test_diesel.cpp
+++ b/tests/unit/test_diesel.cpp
@@ -177,3 +177,32 @@ TEST_CASE("diesel: the 214M railbus's speed control, up to the speed of a button
 	CHECK_FALSE(railbus.SpeedCtrlUnit.IsActive);
 	scenario.check();
 }
+
+TEST_CASE("diesel: the SM42's shunt mode, switched on and off with one move of the switch") {
+	// eu07/maszyna#497: the shunt mode of the diesel-electrics (ShuntMode=1) shares its switch with the motor
+	// overload relay threshold of the electric locomotives (CurrentSwitch()). the SM42 has no such relay, so
+	// the switch sets the shunt mode at the first move, at the controller's zero position only
+	scenario scenario{"diesel/sm42 shunt mode", motion() + traction(), test::track{}};
+	scenario.add("sm42_v1/6d1", 1);
+	REQUIRE(scenario.start_up());
+	auto &sm42{scenario.cab()};
+	REQUIRE(sm42.ShuntModeAllow);
+	CHECK_FALSE(sm42.ShuntMode);
+	scenario.act("shunt mode on");
+	CHECK(sm42.CurrentSwitch(true));
+	CHECK(sm42.ShuntMode);
+	scenario.get_going();
+	scenario.act("shunting power");
+	sm42.AnPos = 0.5;
+	CHECK(sm42.IncMainCtrl(1));
+	scenario.wait(60.0);
+	CHECK(sm42.Vel > 1.0);
+	// not with the controller out of its zero position
+	CHECK_FALSE(sm42.CurrentSwitch(false));
+	CHECK(sm42.ShuntMode);
+	scenario.notch_back(0);
+	scenario.act("shunt mode off");
+	CHECK(sm42.CurrentSwitch(false));
+	CHECK_FALSE(sm42.ShuntMode);
+	scenario.check();
+}