diff --git a/lisa/_kmod.py b/lisa/_kmod.py
index 1e70d301577fc0b7cf27d586133a86f0be3e9431..df1677be7dbeb4d52d19e56501630256e4cec390 100644
--- a/lisa/_kmod.py
+++ b/lisa/_kmod.py
@@ -1042,6 +1042,7 @@ class _KernelBuildEnvConf(SimpleMultiSrcConf):
 
     def _get_key(self):
         return (
+            self.get('overlay-backend'),
             self.get('build-env'),
             self.get('build-env-settings').to_map(),
             sorted(self.get('make-variables', {}).items()),