diff --git a/resources/definitions/uni_base.def.json b/resources/definitions/uni_base.def.json
index 465d49d04f..15d930040e 100644
--- a/resources/definitions/uni_base.def.json
+++ b/resources/definitions/uni_base.def.json
@@ -9,8 +9,8 @@
         "file_formats": "text/x-gcode",
         "first_start_actions": ["MachineSettingsAction"],
         "machine_extruder_trains": {
-            "0": "uni_extruder_1",
-            "1": "uni_extruder_2"
+            "0": "uni_extruder_1st",
+            "1": "uni_extruder_2nd"
         },
         "has_materials": true,
         "preferred_material": "generic_abs_175",
diff --git a/resources/extruders/uni_extruder_1.def.json b/resources/extruders/uni_extruder_1st.def.json
similarity index 94%
rename from resources/extruders/uni_extruder_1.def.json
rename to resources/extruders/uni_extruder_1st.def.json
index 1bf9b1ce71..cd4062892a 100644
--- a/resources/extruders/uni_extruder_1.def.json
+++ b/resources/extruders/uni_extruder_1st.def.json
@@ -8,7 +8,7 @@
     },
 
     "overrides": {
-        "extruder_nr": { "default_value": 0 },
+        "extruder_nr": { "default_value": 0, "maximum_value": "1" },
         "machine_nozzle_size": { "default_value": 0.4 },
         "material_diameter": { "default_value": 1.75 },
         "machine_nozzle_offset_x": { "default_value": 0.0 },
diff --git a/resources/extruders/uni_extruder_2.def.json b/resources/extruders/uni_extruder_2nd.def.json
similarity index 94%
rename from resources/extruders/uni_extruder_2.def.json
rename to resources/extruders/uni_extruder_2nd.def.json
index 6c95efea88..3a09118fc4 100644
--- a/resources/extruders/uni_extruder_2.def.json
+++ b/resources/extruders/uni_extruder_2nd.def.json
@@ -8,7 +8,7 @@
     },
 
     "overrides": {
-        "extruder_nr": { "default_value": 1 },
+        "extruder_nr": { "default_value": 1, "maximum_value": "1" },
         "machine_nozzle_size": { "default_value": 0.4 },
         "material_diameter": { "default_value": 1.75 },
         "machine_nozzle_offset_x": { "default_value": 17.7 },