diff --git a/spacy/errors.py b/spacy/errors.py
index 1a576faee..2b803576c 100644
--- a/spacy/errors.py
+++ b/spacy/errors.py
@@ -128,7 +128,8 @@ class Errors:
             "got {component} (name: '{name}'). If you're using a custom "
             "component factory, double-check that it correctly returns your "
             "initialized component.")
-    E004 = ("Can't set up pipeline component: a factory for '{name}' already exists.")
+    E004 = ("Can't set up pipeline component: a factory for '{name}' already "
+            "exists. Existing factory: {func}. New factory: {new_func}")
     E005 = ("Pipeline component '{name}' returned None. If you're using a "
             "custom component, maybe you forgot to return the processed Doc?")
     E006 = ("Invalid constraints for adding pipeline component. You can only "
diff --git a/spacy/language.py b/spacy/language.py
index 90d2cf81a..1b9a2bfc8 100644
--- a/spacy/language.py
+++ b/spacy/language.py
@@ -396,13 +396,21 @@ class Language:
                 style="default config", name=name, cfg_type=type(default_config)
             )
             raise ValueError(err)
-        internal_name = cls.get_factory_name(name)
-        if internal_name in registry.factories:
-            # We only check for the internal name here – it's okay if it's a
-            # subclass and the base class has a factory of the same name
-            raise ValueError(Errors.E004.format(name=name))
 
         def add_factory(factory_func: Callable) -> Callable:
+            internal_name = cls.get_factory_name(name)
+            if internal_name in registry.factories:
+                # We only check for the internal name here – it's okay if it's a
+                # subclass and the base class has a factory of the same name. We
+                # also only raise if the function is different to prevent raising
+                # if module is reloaded.
+                existing_func = registry.factories.get(internal_name)
+                if not util.is_same_func(factory_func, existing_func):
+                    err = Errors.E004.format(
+                        name=name, func=existing_func, new_func=factory_func
+                    )
+                    raise ValueError(err)
+
             arg_names = util.get_arg_names(factory_func)
             if "nlp" not in arg_names or "name" not in arg_names:
                 raise ValueError(Errors.E964.format(name=name))
@@ -472,6 +480,21 @@ class Language:
             def factory_func(nlp: cls, name: str) -> Callable[[Doc], Doc]:
                 return component_func
 
+            internal_name = cls.get_factory_name(name)
+            if internal_name in registry.factories:
+                # We only check for the internal name here – it's okay if it's a
+                # subclass and the base class has a factory of the same name. We
+                # also only raise if the function is different to prevent raising
+                # if module is reloaded. It's hacky, but we need to check the
+                # existing functure for a closure and whether that's identical
+                # to the component function (because factory_func created above
+                # will always be different, even for the same function)
+                existing_func = registry.factories.get(internal_name)
+                closure = existing_func.__closure__
+                wrapped = [c.cell_contents for c in closure][0] if closure else None
+                if util.is_same_func(wrapped, component_func):
+                    factory_func = existing_func  # noqa: F811
+
             cls.factory(
                 component_name,
                 assigns=assigns,
diff --git a/spacy/tests/pipeline/test_pipe_factories.py b/spacy/tests/pipeline/test_pipe_factories.py
index aa682fefe..f75c9ec8c 100644
--- a/spacy/tests/pipeline/test_pipe_factories.py
+++ b/spacy/tests/pipeline/test_pipe_factories.py
@@ -438,3 +438,26 @@ def test_pipe_factories_from_source_config():
     config = nlp.config["components"]["custom"]
     assert config["factory"] == name
     assert config["arg"] == "world"
+
+
+def test_pipe_factories_decorator_idempotent():
+    """Check that decorator can be run multiple times if the function is the
+    same. This is especially relevant for live reloading because we don't
+    want spaCy to raise an error if a module registering components is reloaded.
+    """
+    name = "test_pipe_factories_decorator_idempotent"
+    func = lambda nlp, name: lambda doc: doc
+    for i in range(5):
+        Language.factory(name, func=func)
+    nlp = Language()
+    nlp.add_pipe(name)
+    Language.factory(name, func=func)
+    # Make sure it also works for component decorator, which creates the
+    # factory function
+    name2 = f"{name}2"
+    func2 = lambda doc: doc
+    for i in range(5):
+        Language.component(name2, func=func2)
+    nlp = Language()
+    nlp.add_pipe(name)
+    Language.component(name2, func=func2)
diff --git a/spacy/util.py b/spacy/util.py
index 8ba164dc1..149bbb21a 100644
--- a/spacy/util.py
+++ b/spacy/util.py
@@ -673,6 +673,25 @@ def get_object_name(obj: Any) -> str:
     return repr(obj)
 
 
+def is_same_func(func1: Callable, func2: Callable) -> bool:
+    """Approximately decide whether two functions are the same, even if their
+    identity is different (e.g. after they have been live reloaded). Mostly
+    used in the @Language.component and @Language.factory decorators to decide
+    whether to raise if a factory already exists. Allows decorator to run
+    multiple times with the same function.
+
+    func1 (Callable): The first function.
+    func2 (Callable): The second function.
+    RETURNS (bool): Whether it's the same function (most likely).
+    """
+    if not callable(func1) or not callable(func2):
+        return False
+    same_name = func1.__qualname__ == func2.__qualname__
+    same_file = inspect.getfile(func1) == inspect.getfile(func2)
+    same_code = inspect.getsourcelines(func1) == inspect.getsourcelines(func2)
+    return all([same_name, same_file, same_code])
+
+
 def get_cuda_stream(
     require: bool = False, non_blocking: bool = True
 ) -> Optional[CudaStream]: