diff --git a/gvm/protocols/gmp/_gmp224.py b/gvm/protocols/gmp/_gmp224.py
index bc263e863..b3e21cd8c 100644
--- a/gvm/protocols/gmp/_gmp224.py
+++ b/gvm/protocols/gmp/_gmp224.py
@@ -3925,14 +3925,13 @@ def modify_task(
             )
         )
 
-    def move_task(
-        self, task_id: EntityID, *, slave_id: EntityID | None = None
-    ) -> T:
+    def move_task(self, task_id: EntityID, *, slave_id: EntityID = "") -> T:
         """Move an existing task to another GMP slave scanner or the master
 
         Args:
             task_id: UUID of the task to be moved
-            slave_id: UUID of the sensor to reassign the task to, empty for master.
+            slave_id: UUID of the sensor to reassign the task to. Defaults to
+                an empty string, which selects the master.
         """
         return self._send_request_and_transform_response(
             Tasks.move_task(task_id, slave_id=slave_id)
diff --git a/gvm/protocols/gmp/_gmpnext.py b/gvm/protocols/gmp/_gmpnext.py
index e5316957c..cd92aaeef 100644
--- a/gvm/protocols/gmp/_gmpnext.py
+++ b/gvm/protocols/gmp/_gmpnext.py
@@ -957,14 +957,13 @@ def modify_task(
             )
         )
 
-    def move_task(
-        self, task_id: EntityID, *, slave_id: EntityID | None = None
-    ) -> T:
+    def move_task(self, task_id: EntityID, *, slave_id: EntityID = "") -> T:
         """Move an existing task to another GMP slave scanner or the master
 
         Args:
             task_id: UUID of the task to be moved
-            slave_id: UUID of the sensor to reassign the task to, empty for master.
+            slave_id: UUID of the sensor to reassign the task to. Defaults to
+                an empty string, which selects the master.
         """
         return self._send_request_and_transform_response(
             Tasks.move_task(
diff --git a/gvm/protocols/gmp/requests/next/_tasks.py b/gvm/protocols/gmp/requests/next/_tasks.py
index 7b1158e38..23ca32b40 100644
--- a/gvm/protocols/gmp/requests/next/_tasks.py
+++ b/gvm/protocols/gmp/requests/next/_tasks.py
@@ -695,24 +695,27 @@ def modify_task(
 
     @classmethod
     def move_task(
-        cls, task_id: EntityID, *, slave_id: EntityID | None = None
+        cls, task_id: EntityID, *, slave_id: EntityID = ""
     ) -> Request:
         """Move an existing task to another GMP slave scanner or the master
 
         Args:
             task_id: UUID of the task to be moved
-            slave_id: UUID of the sensor to reassign the task to, empty for master.
+            slave_id: UUID of the sensor to reassign the task to. Defaults to
+                an empty string, which selects the master.
         """
         if not task_id:
             raise RequiredArgument(
                 function=cls.move_task.__name__, argument="task_id"
             )
+        if slave_id is None:
+            raise RequiredArgument(
+                function=cls.move_task.__name__, argument="slave_id"
+            )
 
         cmd = XmlCommand("move_task")
         cmd.set_attribute("task_id", str(task_id))
-
-        if slave_id is not None:
-            cmd.set_attribute("slave_id", str(slave_id))
+        cmd.set_attribute("slave_id", str(slave_id))
 
         return cmd
 
diff --git a/gvm/protocols/gmp/requests/v224/_tasks.py b/gvm/protocols/gmp/requests/v224/_tasks.py
index f6056cc90..8323db713 100644
--- a/gvm/protocols/gmp/requests/v224/_tasks.py
+++ b/gvm/protocols/gmp/requests/v224/_tasks.py
@@ -354,24 +354,27 @@ def modify_task(
 
     @classmethod
     def move_task(
-        cls, task_id: EntityID, *, slave_id: EntityID | None = None
+        cls, task_id: EntityID, *, slave_id: EntityID = ""
     ) -> Request:
         """Move an existing task to another GMP slave scanner or the master
 
         Args:
             task_id: UUID of the task to be moved
-            slave_id: UUID of the sensor to reassign the task to, empty for master.
+            slave_id: UUID of the sensor to reassign the task to. Defaults to
+                an empty string, which selects the master.
         """
         if not task_id:
             raise RequiredArgument(
                 function=cls.move_task.__name__, argument="task_id"
             )
+        if slave_id is None:
+            raise RequiredArgument(
+                function=cls.move_task.__name__, argument="slave_id"
+            )
 
         cmd = XmlCommand("move_task")
         cmd.set_attribute("task_id", str(task_id))
-
-        if slave_id is not None:
-            cmd.set_attribute("slave_id", str(slave_id))
+        cmd.set_attribute("slave_id", str(slave_id))
 
         return cmd
 
diff --git a/tests/protocols/gmp/requests/v224/test_tasks.py b/tests/protocols/gmp/requests/v224/test_tasks.py
index afe519964..2f785a9d0 100644
--- a/tests/protocols/gmp/requests/v224/test_tasks.py
+++ b/tests/protocols/gmp/requests/v224/test_tasks.py
@@ -664,7 +664,14 @@ def test_move_task(self):
         request = Tasks().move_task("task_id")
         self.assertEqual(
             bytes(request),
-            b'<move_task task_id="task_id"/>',
+            b'<move_task task_id="task_id" slave_id=""/>',
+        )
+
+    def test_move_task_to_master(self):
+        request = Tasks().move_task("task_id", slave_id="")
+        self.assertEqual(
+            bytes(request),
+            b'<move_task task_id="task_id" slave_id=""/>',
         )
 
     def test_move_task_with_slave_id(self):
@@ -681,6 +688,10 @@ def test_move_task_missing_task_id(self):
         with self.assertRaises(RequiredArgument):
             Tasks().move_task(None)
 
+    def test_move_task_none_slave_id(self):
+        with self.assertRaises(RequiredArgument):
+            Tasks().move_task("task_id", slave_id=None)
+
     def test_start_task(self):
         request = Tasks().start_task("task_id")
         self.assertEqual(
diff --git a/tests/protocols/gmpnext/entities/tasks/test_move_task.py b/tests/protocols/gmpnext/entities/tasks/test_move_task.py
index efc58af50..e690b7ecb 100644
--- a/tests/protocols/gmpnext/entities/tasks/test_move_task.py
+++ b/tests/protocols/gmpnext/entities/tasks/test_move_task.py
@@ -10,7 +10,16 @@ class GmpMoveTaskTestMixin:
     def test_move_task(self):
         self.gmp.move_task("a1")
 
-        self.connection.send.has_been_called_with(b'<move_task task_id="a1"/>')
+        self.connection.send.has_been_called_with(
+            b'<move_task task_id="a1" slave_id=""/>'
+        )
+
+    def test_move_task_to_master(self):
+        self.gmp.move_task("a1", slave_id="")
+
+        self.connection.send.has_been_called_with(
+            b'<move_task task_id="a1" slave_id=""/>'
+        )
 
     def test_move_task_to_slave(self):
         self.gmp.move_task("a1", slave_id="s1")
@@ -25,3 +34,7 @@ def test_missing_id(self):
 
         with self.assertRaises(GvmError):
             self.gmp.move_task("")
+
+    def test_none_slave_id(self):
+        with self.assertRaises(GvmError):
+            self.gmp.move_task("a1", slave_id=None)
diff --git a/tests/protocols/gmpv224/entities/tasks/test_move_task.py b/tests/protocols/gmpv224/entities/tasks/test_move_task.py
index 6898abbc6..3c0095f64 100644
--- a/tests/protocols/gmpv224/entities/tasks/test_move_task.py
+++ b/tests/protocols/gmpv224/entities/tasks/test_move_task.py
@@ -10,7 +10,16 @@ class GmpMoveTaskTestMixin:
     def test_move_task(self):
         self.gmp.move_task("a1")
 
-        self.connection.send.has_been_called_with(b'<move_task task_id="a1"/>')
+        self.connection.send.has_been_called_with(
+            b'<move_task task_id="a1" slave_id=""/>'
+        )
+
+    def test_move_task_to_master(self):
+        self.gmp.move_task("a1", slave_id="")
+
+        self.connection.send.has_been_called_with(
+            b'<move_task task_id="a1" slave_id=""/>'
+        )
 
     def test_move_task_to_slave(self):
         self.gmp.move_task("a1", slave_id="s1")
@@ -25,3 +34,7 @@ def test_missing_id(self):
 
         with self.assertRaises(GvmError):
             self.gmp.move_task("")
+
+    def test_none_slave_id(self):
+        with self.assertRaises(GvmError):
+            self.gmp.move_task("a1", slave_id=None)