diff --git a/tools/exekall/exekall/_utils.py b/tools/exekall/exekall/_utils.py
index a805f087ed514d113451b76d2a148f228eca672f..dc71bc93e92748f12653320dff6dd346773c0c4f 100644
--- a/tools/exekall/exekall/_utils.py
+++ b/tools/exekall/exekall/_utils.py
@@ -1043,16 +1043,6 @@ def get_recursive_module_set(module_set, package_set, visited_module_set=None):
     """
     visited_modules = set(visited_module_set) if visited_module_set else set()
 
-    def select_module(module):
-        # We only recurse into modules that are part of the given set
-        # of packages
-        return any(
-            # Either a submodule of one of the packages or one of the
-            # packages themselves
-            get_package(module) == package
-            for package in package_set
-        )
-
     def _get_recursive_module_set(modules, module_set, package_set):
         for module in modules:
             if not isinstance(module, types.ModuleType):
@@ -1063,7 +1053,9 @@ def get_recursive_module_set(module_set, package_set, visited_module_set=None):
             else:
                 visited_modules.add(module)
 
-            if select_module(module):
+            # We only recurse into modules that are part of the given set
+            # of packages
+            if get_package(module) in package_set:
                 module_set.add(module)
                 _get_recursive_module_set(vars(module).values(), module_set, package_set)
 
diff --git a/tools/exekall/exekall/utils.py b/tools/exekall/exekall/utils.py
index efd940d5b32363c02a7654f20305070ceb6abde1..655bbe7948e92f2e6c385c57eb03bf4915f35e4e 100644
--- a/tools/exekall/exekall/utils.py
+++ b/tools/exekall/exekall/utils.py
@@ -34,6 +34,8 @@ def get_callable_set(module_set, verbose=False):
     """
     Get the set of callables defined in all modules of ``module_set``.
 
+    We ignore any callable that is defined outside of the modules' package.
+
     :param module_set: Set of modules to scan.
     :type module_set: set(types.ModuleType)
     """
@@ -52,6 +54,7 @@ def get_callable_set(module_set, verbose=False):
             callable_set_ = _get_callable_set(
                 module,
                 visited_obj_set,
+                package_set=package_set,
                 verbose=verbose,
             )
 
@@ -97,7 +100,7 @@ def _get_members(*args, **kwargs):
         warnings.simplefilter(action='ignore')
         return inspect.getmembers(*args, **kwargs)
 
-def _get_callable_set(namespace, visited_obj_set, verbose):
+def _get_callable_set(namespace, visited_obj_set, package_set, verbose):
     """
     :param namespace: Module or class
     """
@@ -116,19 +119,26 @@ def _get_callable_set(namespace, visited_obj_set, verbose):
             predicate=callable
         )
     ]
+
     if isinstance(namespace, type):
         attributes.append(namespace)
 
+    def select(attr):
+        module = inspect.getmodule(attr)
+        return (
+            # Module of builtins is None
+            module is None or
+            # skip internal classes that may end up being exposed as a global
+            module is not engine and
+            get_package(module) in package_set
+        )
+
+    visited_obj_set.update(attributes)
     attributes = [
         attr
         for attr in attributes
-        if (
-            id(attr) not in visited_obj_set and
-            # skip internal classes that may end up being exposed as a global
-            inspect.getmodule(attr) is not engine
-        )
+        if id(attr) not in visited_obj_set and select(attr)
     ]
-    visited_obj_set.update(attributes)
 
     for callable_ in attributes:
         # Explore the class attributes as well for nested types
@@ -148,7 +158,7 @@ def _get_callable_set(namespace, visited_obj_set, verbose):
             )
         ):
             callable_pool.update(
-                _get_callable_set(callable_, visited_obj_set, verbose)
+                _get_callable_set(callable_, visited_obj_set, package_set, verbose)
             )
 
         # Functions defined in a class are methods, and have to be wrapped so