diff --git a/tools/exekall/exekall/_utils.py b/tools/exekall/exekall/_utils.py
index dcb6e89678b23a8fdf7ff88699d633eeccfe2569..a805f087ed514d113451b76d2a148f228eca672f 100644
--- a/tools/exekall/exekall/_utils.py
+++ b/tools/exekall/exekall/_utils.py
@@ -253,8 +253,12 @@ class ExceptionPickler(pickle.Pickler):
                 raise KeyError
 
     def __init__(self, *args, **kwargs):
-        self.dispatch_table = self._DispatchTable(self)
+
+        # Due to this issue, it is critical that "dispatch_table" is set after
+        # calling super().__init__
+        # https://bugs.python.org/issue45830
         super().__init__(*args, **kwargs)
+        self.dispatch_table = self._DispatchTable(self)
 
     @staticmethod
     def _make_excep(excep_cls, dct):
@@ -314,25 +318,30 @@ class ExceptionPickler(pickle.Pickler):
         pickler = cls(f, **kwargs)
         return pickler.dump(obj)
 
+    @classmethod
+    def is_serializable(cls, obj, raise_excep=False):
+        """
+        Try to Pickle the object to see if that raises any exception.
+        """
+        class DevNull:
+            def write(self, _):
+                pass
+        try:
+            # This may be slow for big objects but it is the only way to be
+            # sure it can actually be serialized
+            cls.dump_file(DevNull(), obj)
+        except (TypeError, pickle.PickleError, AttributeError) as e:
+            debug('Cannot serialize instance of {}: {}'.format(
+                type(obj).__qualname__, str(e)
+            ))
+            if raise_excep:
+                raise NotSerializableError(obj) from e
+            return False
+        else:
+            return True
+
 
-def is_serializable(obj, raise_excep=False):
-    """
-    Try to Pickle the object to see if that raises any exception.
-    """
-    stream = io.StringIO()
-    try:
-        # This may be slow for big objects but it is the only way to be sure
-        # it can actually be serialized
-        ExceptionPickler.dump_bytestring(obj)
-    except (TypeError, pickle.PickleError, AttributeError) as e:
-        debug('Cannot serialize instance of {}: {}'.format(
-            type(obj).__qualname__, str(e)
-        ))
-        if raise_excep:
-            raise NotSerializableError(obj) from e
-        return False
-    else:
-        return True
+is_serializable = ExceptionPickler.is_serializable
 
 
 def once(callable_):