diff --git a/exasol_advanced_analytics_framework/udf_framework/dynamic_modules.py b/exasol_advanced_analytics_framework/udf_framework/dynamic_modules.py
index 8086ea4d..899e00ad 100644
--- a/exasol_advanced_analytics_framework/udf_framework/dynamic_modules.py
+++ b/exasol_advanced_analytics_framework/udf_framework/dynamic_modules.py
@@ -4,6 +4,15 @@
 from types import ModuleType
 
 
+def _create_module(name: str) -> ModuleType:
+    spec = importlib.machinery.ModuleSpec(name, None)
+    return importlib.util.module_from_spec(spec)
+
+
+def _register_module_for_import(name: str, mod: ModuleType):
+    sys.modules[name] = mod
+
+
 def create_module(name: str) -> ModuleType:
     """
     Dynamically create a python module using the specified name and
@@ -12,9 +21,10 @@ def create_module(name: str) -> ModuleType:
     Additionally add a function add_to_module() to the module enabling other
     code to add classes and functions to the module.
     """
-    spec = importlib.machinery.ModuleSpec(name, None)
-    mod = importlib.util.module_from_spec(spec)
-    sys.modules[name] = mod
+    mod = sys.modules.get(name)
+    if mod is None:
+        mod = _create_module(name)
+        _register_module_for_import(name, mod)
 
     def add_to_module(object: Any):
         object.__module__ = name
diff --git a/tests/unit_tests/udf_framework/test_dynamic_modules.py b/tests/unit_tests/udf_framework/test_dynamic_modules.py
index ba1db1c0..b4f08a09 100644
--- a/tests/unit_tests/udf_framework/test_dynamic_modules.py
+++ b/tests/unit_tests/udf_framework/test_dynamic_modules.py
@@ -24,3 +24,17 @@ def test_add_function():
     xx2.add_to_module(example_function)
     assert xx2.example_function() == "example_function return value" \
         and example_function.__module__ == "xx2"
+
+
+def test_add_function_to_existing_module():
+    def my_func():
+        return "another return value"
+
+    mod1 = create_module("xx2")
+    import xx2
+    xx2.add_to_module(example_function)
+    mod2 = create_module("xx2")
+    assert mod2 == mod1
+    xx2.add_to_module(my_func)
+    assert xx2.example_function() == "example_function return value" \
+        and xx2.my_func() == "another return value"