diff --git a/src/Mod/Fem/FemTools.py b/src/Mod/Fem/FemTools.py
index 0354ac89c..65b07b407 100644
--- a/src/Mod/Fem/FemTools.py
+++ b/src/Mod/Fem/FemTools.py
@@ -340,7 +340,7 @@ class FemTools(QtCore.QRunnable, QtCore.QObject):
                 message += "FEM mesh has no volume and no shell elements, either define a beam section or provide a FEM mesh with volume elements.\n"
             if self.mesh.FemMesh.VolumeCount == 0 and self.mesh.FemMesh.FaceCount == 0 and self.mesh.FemMesh.EdgeCount == 0:
                 message += "FEM mesh has neither volume nor shell or edge elements. Provide a FEM mesh with elements!\n"
-        # materials_linear
+        # materials linear and nonlinear
         if not self.materials_linear:
             message += "No material object defined in the analysis\n"
         has_no_references = False
@@ -365,6 +365,14 @@ class FemTools(QtCore.QRunnable, QtCore.QObject):
                     message += "Thermomechanical analysis: No ThermalExpansionCoefficient defined for at least one material.\n"
                 if 'SpecificHeat' not in mat_map:
                     message += "Thermomechanical analysis: No SpecificHeat defined for at least one material.\n"
+        for m in self.materials_linear:
+            has_nonlinear_material = False
+            for nlm in self.materials_nonlinear:
+                if nlm['Object'].LinearBaseMaterial == m['Object']:
+                    if has_nonlinear_material is False:
+                        has_nonlinear_material = True
+                    else:
+                        message += "At least two nonlinear materials use the same linear base material. Only one nonlinear material for each linear material allowed. \n"
         # constraints
         if self.analysis_type == "static":
             if not (self.fixed_constraints or self.displacement_constraints):
diff --git a/src/Mod/Fem/_CommandMaterialMechanicalNonlinear.py b/src/Mod/Fem/_CommandMaterialMechanicalNonlinear.py
index 6d228585f..3067bb192 100644
--- a/src/Mod/Fem/_CommandMaterialMechanicalNonlinear.py
+++ b/src/Mod/Fem/_CommandMaterialMechanicalNonlinear.py
@@ -47,13 +47,19 @@ class _CommandMaterialMechanicalNonlinear(FemCommands):
         sel = FreeCADGui.Selection.getSelection()
         if len(sel) == 1 and sel[0].isDerivedFrom("App::MaterialObjectPython"):
             lin_mat_obj = sel[0]
-            # TODO --> check print
-            print "check if an nonlinear material exists which referes to the selected material already, becaue for each linear material only one nonlinear material is allowed !!!\n"
-            string_lin_mat_obj = "App.ActiveDocument.getObject('" + lin_mat_obj.Name + "')"
-            command_to_run = "FemGui.getActiveAnalysis().Member = FemGui.getActiveAnalysis().Member + [FemMaterialMechanicalNonlinear.makeFemMaterialMechanicalNonlinear(" + string_lin_mat_obj + ")]"
-            FreeCAD.ActiveDocument.openTransaction("Create FemMaterialMechanicalNonlinear")
-            FreeCADGui.addModule("FemMaterialMechanicalNonlinear")
-            FreeCADGui.doCommand(command_to_run)
+            # check if an nonlinear material exists which is based on the selected material already
+            allow_nonlinear_material = True
+            for o in FreeCAD.ActiveDocument.Objects:
+                if hasattr(o, "Proxy") and o.Proxy is not None and o.Proxy.Type == "FemMaterialMechanicalNonlinear" and o.LinearBaseMaterial == lin_mat_obj:
+                    FreeCAD.Console.PrintError(o.Name + ' is based on the selected material: ' + lin_mat_obj.Name + '. Only one nonlinear object for each material allowed.\n')
+                    allow_nonlinear_material = False
+                    break
+            if allow_nonlinear_material:
+                string_lin_mat_obj = "App.ActiveDocument.getObject('" + lin_mat_obj.Name + "')"
+                command_to_run = "FemGui.getActiveAnalysis().Member = FemGui.getActiveAnalysis().Member + [FemMaterialMechanicalNonlinear.makeFemMaterialMechanicalNonlinear(" + string_lin_mat_obj + ")]"
+                FreeCAD.ActiveDocument.openTransaction("Create FemMaterialMechanicalNonlinear")
+                FreeCADGui.addModule("FemMaterialMechanicalNonlinear")
+                FreeCADGui.doCommand(command_to_run)
 
 if FreeCAD.GuiUp:
     FreeCADGui.addCommand('Fem_MaterialMechanicalNonlinear', _CommandMaterialMechanicalNonlinear())