diff --git a/weldx_widgets/tests/test_gas.py b/weldx_widgets/tests/test_gas.py
index fb220f1..e241a58 100644
--- a/weldx_widgets/tests/test_gas.py
+++ b/weldx_widgets/tests/test_gas.py
@@ -3,8 +3,6 @@
 
 from weldx import WeldxFile
 from weldx_widgets import WidgetShieldingGas
-from weldx_widgets.tests.util import voila_language
-from weldx_widgets.widget_gas import WidgetSimpleGasSelection
 
 
 @pytest.mark.parametrize("write_file", (True, False))
@@ -28,10 +26,3 @@ def test_import_export(write_file):
     w2 = WidgetShieldingGas()
     w2.from_tree(tree)
     assert w2.to_tree() == tree
-
-
-def test_lang():
-    """Test translation."""
-    with voila_language(lang="de"):
-        w = WidgetSimpleGasSelection()
-    assert "Sauerstoff" in w.gas_list
diff --git a/weldx_widgets/widget_base.py b/weldx_widgets/widget_base.py
index 200968b..7df366d 100644
--- a/weldx_widgets/widget_base.py
+++ b/weldx_widgets/widget_base.py
@@ -7,8 +7,27 @@
 
 from weldx.asdf.util import get_schema_path
 
+def metaclass_resolver(*classes):
+    """Merge multiple meta classes."""
+    # Does something like this:
+    # https://coderedirect.com/questions/163000/multiple-inheritance-metaclass-conflict
+    metaclass = tuple(set(type(cls) for cls in classes))
 
-class WidgetBase:
+    def cls_name(classes):
+        return "_".join(mcls.__name__ for mcls in classes)
+
+    metaclass = (
+        metaclass[0]
+        if len(metaclass) == 1
+        else type(cls_name(metaclass), metaclass, {})
+    )  # class M_C
+    return metaclass(cls_name(classes), classes, {})  # class C
+
+class _merged_meta(type(abc.ABC)):  # avoid metaclass conflict.
+    pass
+
+
+class WidgetBase(abc.ABC, metaclass=_merged_meta):
     """Base class for weldx widgets."""
 
     def copy(self):
@@ -41,7 +60,7 @@ def _ipython_display_(self):
 margin = ""  # "10px"
 
 
-class WidgetMyHBox(HBox, WidgetBase):
+class WidgetMyHBox(metaclass_resolver(HBox, WidgetBase)):
     """Wrap around a HBox sharing a common layout."""
 
     def __init__(self, *args, **kwargs):
@@ -56,7 +75,7 @@ def __init__(self, *args, **kwargs):
         super().__init__(*args, **kwargs)
 
 
-class WidgetMyVBox(VBox, WidgetBase):
+class WidgetMyVBox(metaclass_resolver(VBox, WidgetBase)):
     """Wrap around a VBox sharing a common layout."""
 
     def __init__(self, *args, **kwargs):
diff --git a/weldx_widgets/widget_evaluate.py b/weldx_widgets/widget_evaluate.py
index 883429d..92265df 100644
--- a/weldx_widgets/widget_evaluate.py
+++ b/weldx_widgets/widget_evaluate.py
@@ -26,7 +26,7 @@
     Trace,
     WeldxFile,
 )
-from weldx_widgets.widget_base import WidgetBase, WidgetSimpleOutput
+from weldx_widgets.widget_base import WidgetBase, WidgetSimpleOutput, metaclass_resolver
 from weldx_widgets.widget_factory import make_title
 from weldx_widgets.widget_measurement import WidgetMeasurement, WidgetMeasurementChain
 
@@ -85,7 +85,7 @@ def dims_as_coords(arr):
     data.coordinates = filtered
 
 
-class WidgetEvaluateSinglePassWeld(Tab, WidgetBase):
+class WidgetEvaluateSinglePassWeld(metaclass_resolver(Tab, WidgetBase)):
     """Aggregate info of passed file in several tabs."""
 
     def __init__(self, file: WeldxFile):
diff --git a/weldx_widgets/widget_gmaw.py b/weldx_widgets/widget_gmaw.py
index b1e0c00..b18a486 100644
--- a/weldx_widgets/widget_gmaw.py
+++ b/weldx_widgets/widget_gmaw.py
@@ -38,7 +38,7 @@ def plot_gmaw(gmaw, t):
     fig, ax = plt.subplots(nrows=n, sharex="all", figsize=(_DEFAULT_FIGWIDTH, 2 * n))
     for i, k in enumerate(pars):
         parplot(pars[k], t, k, ax[i])
-    ax[-1].set_xlabel("time") + " / s"
+    ax[-1].set_xlabel("time / s")
     ax[0].set_title(title, loc="left")
 
     # ipympl_style(fig)