diff --git a/src/main/java/com/powsybl/openloadflow/network/NameSlackBusSelector.java b/src/main/java/com/powsybl/openloadflow/network/NameSlackBusSelector.java
index 901d1cbc8e..578d22b7a4 100644
--- a/src/main/java/com/powsybl/openloadflow/network/NameSlackBusSelector.java
+++ b/src/main/java/com/powsybl/openloadflow/network/NameSlackBusSelector.java
@@ -6,8 +6,6 @@
  */
 package com.powsybl.openloadflow.network;
 
-import com.powsybl.commons.PowsyblException;
-
 import java.util.*;
 import java.util.function.Function;
 import java.util.stream.Collectors;
@@ -55,6 +53,7 @@ public SelectedSlackBus select(List<LfBus> buses) {
                 }
             }
         }
-        throw new PowsyblException("None of the buses or voltage levels " + busesOrVoltageLevelsIds + " have been found");
+        // fallback to automatic selection among all buses
+        return secondLevelSelector.select(buses);
     }
 }
diff --git a/src/test/java/com/powsybl/openloadflow/OpenLoadFlowParametersTest.java b/src/test/java/com/powsybl/openloadflow/OpenLoadFlowParametersTest.java
index 8ebf0ab48e..bc23d03281 100644
--- a/src/test/java/com/powsybl/openloadflow/OpenLoadFlowParametersTest.java
+++ b/src/test/java/com/powsybl/openloadflow/OpenLoadFlowParametersTest.java
@@ -8,7 +8,6 @@
 
 import com.google.common.jimfs.Configuration;
 import com.google.common.jimfs.Jimfs;
-import com.powsybl.commons.PowsyblException;
 import com.powsybl.commons.config.InMemoryPlatformConfig;
 import com.powsybl.commons.config.MapModuleConfig;
 import com.powsybl.commons.config.PlatformConfig;
@@ -35,6 +34,7 @@
 import java.util.Map;
 
 import static org.junit.jupiter.api.Assertions.*;
+import static org.junit.jupiter.api.Assertions.assertEquals;
 
 /**
  * @author Jérémy Labous <jlabous at silicom.fr>
@@ -154,8 +154,7 @@ void testNameSlackBusSelector() throws IOException {
         assertEquals(SlackBusSelectionMode.NAME, olfParameters.getSlackBusSelectionMode());
         List<LfNetwork> lfNetworks = Networks.load(EurostagTutorialExample1Factory.create(), SlackBusSelector.fromMode(olfParameters.getSlackBusSelectionMode(), olfParameters.getSlackBusesIds(), olfParameters.getPlausibleActivePowerLimit()));
         LfNetwork lfNetwork = lfNetworks.get(0);
-        PowsyblException thrown = assertThrows(PowsyblException.class, lfNetwork::getSlackBus);
-        assertEquals("None of the buses or voltage levels [???] have been found", thrown.getMessage());
+        assertEquals("VLHV1_0", lfNetwork.getSlackBus().getId()); // fallback to automatic method.
     }
 
     @Test
diff --git a/src/test/java/com/powsybl/openloadflow/network/NameSlackBusSelectorTest.java b/src/test/java/com/powsybl/openloadflow/network/NameSlackBusSelectorTest.java
index 1ab2951f75..d05e15fd75 100644
--- a/src/test/java/com/powsybl/openloadflow/network/NameSlackBusSelectorTest.java
+++ b/src/test/java/com/powsybl/openloadflow/network/NameSlackBusSelectorTest.java
@@ -6,7 +6,6 @@
  */
 package com.powsybl.openloadflow.network;
 
-import com.powsybl.commons.PowsyblException;
 import com.powsybl.iidm.network.Network;
 import com.powsybl.iidm.network.test.EurostagTutorialExample1Factory;
 import com.powsybl.openloadflow.network.impl.Networks;
@@ -16,7 +15,6 @@
 import java.util.List;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
-import static org.junit.jupiter.api.Assertions.assertThrows;
 
 /**
  * @author Geoffroy Jamgotchian <geoffroy.jamgotchian at rte-france.com>
@@ -42,15 +40,6 @@ void test() {
         assertEquals("VLLOAD_0", lfNetwork.getSlackBus().getId());
     }
 
-    @Test
-    void errorTest() {
-        NameSlackBusSelector slackBusSelector = new NameSlackBusSelector("???");
-        List<LfNetwork> lfNetworks = Networks.load(network, slackBusSelector);
-        LfNetwork lfNetwork = lfNetworks.get(0);
-        assertThrows(PowsyblException.class, () -> lfNetwork.getSlackBus(),
-            "Slack bus '???' not found");
-    }
-
     @Test
     void voltageLevelIdTest() {
         List<LfNetwork> lfNetworks = Networks.load(network, new NameSlackBusSelector("VLGEN"));