diff --git a/Qt.py b/Qt.py
index 17a9ff6a..8ee4e9e4 100644
--- a/Qt.py
+++ b/Qt.py
@@ -874,6 +874,23 @@ def get_arg(index):
     return app.translate(*sanitized_args)
 
 
+def _headerToModule(header):
+    """
+    Translate a header file to python module path
+    foo/bar.h => foo.bar
+    """
+
+    # Only manipulate header files, identified by the `.h` ext.
+    if header.endswith(".h") is False:
+        return header
+
+    # Remove header extension
+    module = os.path.splitext(header)[0]
+
+    # Replace os separator by python module separator
+    return module.replace("/", ".").replace("\\", ".")
+
+
 def _loadUi(uifile, baseinstance=None):
     """Dynamically load a user interface from the given `uifile`
 
@@ -925,22 +942,6 @@ def _loadCustomWidgets(self, etree):
                 objects. Then we can directly use them in createWidget method.
                 """
 
-                def headerToModule(header):
-                    """
-                    Translate a header file to python module path
-                    foo/bar.h => foo.bar
-                    """
-
-                    if header.endswith(".h") is False:
-                        # Only manipulate header files, identified by the `.h` ext.
-                        return header
-
-                    # Remove header extension
-                    module = os.path.splitext(header)[0]
-
-                    # Replace os separator by python module separator
-                    return module.replace("/", ".").replace("\\", ".")
-
                 custom_widgets = etree.find("customwidgets")
 
                 if custom_widgets is None:
@@ -949,13 +950,7 @@ def headerToModule(header):
                 for custom_widget in custom_widgets:
                     class_name = custom_widget.find("class").text
                     header = custom_widget.find("header").text
-                    try:
-                        header = headerToModule(header)
-                        module = importlib.import_module(header)
-                    except ImportError as _error:
-                        # ReRaising the ImportError with a more informative
-                        # message to aid in the creation of Tests for this case.
-                        raise ImportError("No module named '%s'" % header)
+                    module = importlib.import_module(_headerToModule(header))
                     self.custom_widgets[class_name] = getattr(module,
                                                               class_name)
 
diff --git a/tests.py b/tests.py
index 18bee443..d7798039 100644
--- a/tests.py
+++ b/tests.py
@@ -449,25 +449,10 @@ def test_load_ui_customwidget():
     app.exit()
 
 
-def _rewrite_file(file, current, provided):
-    with open(file, "r") as f:
-        new = f.read().replace(
-            "<header>" + current + "</header>",
-            "<header>" + provided + "</header>"
-        )
-    with open(self.ui_qpycustomwidget, "w") as f:
-        f.write(new)
-
-
-def test_load_ui_pycustomwidget():
-    """Tests to see if loadUi loads a custom widget from different sources,
-    such as a Python path or a .h path can be parsed properly.
-
-    The structure of the current code does not provide direct access to the
-    headertomodule function. Instead, the test updates the temp.ui file to
-    contain a different header and tries to load the UI. All cases are
-    designed to trigger a ModuleImport Exception which reports the path
-    expected.
+def test_headerToModule():
+    """
+    Tests to see if headerToModule manipulates the path passed in appropriately.
+    - It should only affect `Header` files and paths, marked with an .h extension.
     """
 
     path_tests = {
@@ -489,30 +474,13 @@ def test_load_ui_pycustomwidget():
         "path/to/module": "path/to/module",
         "module.py": "module.py",
     }
-    import sys
-    from Qt import QtWidgets, QtCompat
 
-    app = QtWidgets.QApplication(sys.argv)
-    win = QtWidgets.QMainWindow()
+    import Qt
 
-    current = "tests"
     for provided, expected in path_tests.items():
-        _rewrite_file(self.ui_qpycustomwidget, current, provided)
-        current = provided
+        result = Qt._headerToModule(provided)
+        assert result == expected, "Provided: %s expected: %s got: %s" % (provided, expected, result)
 
-        try:
-            # actual test
-            QtCompat.loadUi(self.ui_qpycustomwidget, win)
-
-        except ImportError as error:
-            # Since the loadUi is a blackbox it is not possible to test the
-            # `headertomodule` function directly. Test if the ImportError
-            # error contains the correct import path.
-            result = str(error).split("'")[1]
-            assert result == expected, (
-                    "Provided: %s expected: %s got: %s" % (provided, expected, result)
-            )
-    app.exit()
 
 def test_load_ui_invalidpath():
     """Tests to see if loadUi successfully fails on invalid paths"""