diff --git a/plugins/VersionUpgrade/VersionUpgrade25to26/VersionUpgrade25to26.py b/plugins/VersionUpgrade/VersionUpgrade25to26/VersionUpgrade25to26.py
index 2c598ad766..e1c14be2e1 100644
--- a/plugins/VersionUpgrade/VersionUpgrade25to26/VersionUpgrade25to26.py
+++ b/plugins/VersionUpgrade/VersionUpgrade25to26/VersionUpgrade25to26.py
@@ -127,7 +127,12 @@ class VersionUpgrade25to26(VersionUpgrade):
         machine_id = parser["general"]["id"]
         quality_container_id = parser["containers"]["2"]
         material_container_id = parser["containers"]["3"]
-        definition_container_id = parser["containers"]["6"]
+
+        # we don't have definition_changes container in 2.5
+        if "6" in parser["containers"]:
+            definition_container_id = parser["containers"]["6"]
+        else:
+            definition_container_id = parser["containers"]["5"]
 
         if definition_container_id == "custom" and not self._checkCustomFdmPrinterHasExtruderStack(machine_id):
             # go through all extruders and make sure that this custom FDM printer has 8 extruder stacks.