diff --git a/src/cpl_reactive_extensions/observable.py b/src/cpl_reactive_extensions/observable.py
index b3534576..809c1ad7 100644
--- a/src/cpl_reactive_extensions/observable.py
+++ b/src/cpl_reactive_extensions/observable.py
@@ -1,4 +1,4 @@
-from typing import Callable, Union
+from typing import Callable, Union, Optional
 
 from cpl_reactive_extensions.observer import Observer
 
@@ -31,10 +31,12 @@ class Observable:
     def subscribe(
         self, observer_or_next: Union[Callable, Observer], on_error: Callable = None, on_complete: Callable = None
     ) -> Observer:
+        observable: Optional[Observable] = None
+        if isinstance(observer_or_next, Observable):
+            observable = observer_or_next
+
         if isinstance(observer_or_next, Callable):
             observer = Observer(observer_or_next, on_error, on_complete)
-        elif isinstance(observer_or_next, Observable):
-            observer = observer_or_next
         else:
             observer = observer_or_next
 
@@ -42,8 +44,8 @@ class Observable:
             self._observers.append(observer)
             return observer
 
-        if len(observer._observers) > 0:
-            for observer in observer._observers:
+        if observable is not None and len(observable._observers) > 0:
+            for observer in observable._observers:
                 self._call(observer)
         else:
             self._call(observer)
diff --git a/src/cpl_reactive_extensions/observer.py b/src/cpl_reactive_extensions/observer.py
index a9fe0f4e..0c9dee24 100644
--- a/src/cpl_reactive_extensions/observer.py
+++ b/src/cpl_reactive_extensions/observer.py
@@ -16,6 +16,9 @@ class Observer:
         return self._closed
 
     def next(self, value: T):
+        if self._closed:
+            raise Exception("Observer is closed")
+
         self._on_next(value)
 
     def error(self, ex: Exception):
@@ -24,6 +27,7 @@ class Observer:
         self._on_error(ex)
 
     def complete(self):
+        self._closed = True
         if self._on_complete is None:
             return
 
diff --git a/unittests/unittests_reactive_extenstions/reactive_test_case.py b/unittests/unittests_reactive_extenstions/reactive_test_case.py
index fc30f812..7b590394 100644
--- a/unittests/unittests_reactive_extenstions/reactive_test_case.py
+++ b/unittests/unittests_reactive_extenstions/reactive_test_case.py
@@ -1,3 +1,4 @@
+import time
 import traceback
 import unittest
 from threading import Timer
@@ -15,7 +16,7 @@ class ReactiveTestCase(unittest.TestCase):
 
     def _on_error(self, ex: Exception):
         tb = traceback.format_exc()
-        Console.error(f"Somthing went wrong: {ex}", tb)
+        Console.error(f"Got error from observable: {ex}", tb)
         self._error = True
 
     def _on_complete(self):
@@ -67,6 +68,19 @@ class ReactiveTestCase(unittest.TestCase):
 
         Timer(1.0, complete).start()
 
+        time.sleep(2)
+
+        def _test_complete(x: Observer):
+            x.next(1)
+            x.next(2)
+            x.complete()
+            x.next(3)
+
+        observable2 = Observable(_test_complete)
+
+        observable2.subscribe(lambda x: x, self._on_error)
+        self.assertTrue(self._error)
+
     def test_observable_from(self):
         expected_x = 1
 
@@ -93,10 +107,10 @@ class ReactiveTestCase(unittest.TestCase):
                 expected_x = 1
 
         subject = Subject(int)
-        subject.subscribe(_next, self._on_error, self._on_complete)
-        subject.subscribe(_next, self._on_error, self._on_complete)
+        subject.subscribe(_next, self._on_error)
+        subject.subscribe(_next, self._on_error)
 
         observable = Observable.from_list([1, 2, 3])
-        observable.subscribe(subject, self._on_error, self._on_complete)
+        observable.subscribe(subject, self._on_error)
 
         self.assertFalse(self._error)