diff --git a/fractal/__init__.py b/fractal/__init__.py
index 14561dc..e8e8a9b 100644
--- a/fractal/__init__.py
+++ b/fractal/__init__.py
@@ -1,6 +1,6 @@
 """Fractal is a scaffolding toolkit for building SOLID logic for your Python applications."""
 
-__version__ = "5.1.0"
+__version__ = "5.2.0"
 
 from abc import ABC
 
diff --git a/fractal/core/event_sourcing/event.py b/fractal/core/event_sourcing/event.py
index c800804..78ab175 100644
--- a/fractal/core/event_sourcing/event.py
+++ b/fractal/core/event_sourcing/event.py
@@ -45,5 +45,5 @@ def to_command(self):
 
 class EventCommandMapper(ABC):
     @abstractmethod
-    def mappers(self) -> Dict[Type[Event], List[Callable[[Event], Command]]]:
+    def mappers(self) -> Dict[Type[Event], List[Callable[[Event], List[Command]]]]:
         raise NotImplementedError
diff --git a/fractal/core/event_sourcing/projectors/command_bus_projector.py b/fractal/core/event_sourcing/projectors/command_bus_projector.py
index 35a1cec..d49e16f 100644
--- a/fractal/core/event_sourcing/projectors/command_bus_projector.py
+++ b/fractal/core/event_sourcing/projectors/command_bus_projector.py
@@ -25,4 +25,8 @@ def project(self, id: str, event: Union[SendingEvent, ReceivingEvent]):
             self.command_bus_func().handle(event.to_command())
         elif event.__class__ in self.mappers:
             for mapper in self.mappers[event.__class__]:
-                self.command_bus_func().handle(mapper(event))
+                commands = mapper(event)
+                if commands != list:  # backwards compatibility
+                    commands = [commands]
+                for command in commands:
+                    self.command_bus_func().handle(command)
diff --git a/pyproject.toml b/pyproject.toml
index 79f3d4d..65487a0 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,6 +1,6 @@
 [tool.poetry]
 name = "fractal-toolkit"
-version = "5.1.0"
+version = "5.2.0"
 description = "Fractal is a scaffolding toolkit for building SOLID logic for your Python applications."
 authors = ["Douwe van der Meij <douwe@karibu-online.nl>"]