diff --git a/apis/configuration/slo_controller_config.go b/apis/configuration/slo_controller_config.go
index d4a2ab99b..03cf238de 100644
--- a/apis/configuration/slo_controller_config.go
+++ b/apis/configuration/slo_controller_config.go
@@ -152,7 +152,7 @@ func (in *ExtensionCfg) DeepCopy() *ExtensionCfg {
 // +k8s:deepcopy-gen=false
 type NodeExtensionStrategy struct {
 	NodeCfgProfile `json:",inline"`
-	NodeStrategy   interface{} // for third-party extension
+	NodeStrategy   interface{} `json:",inline"` // for third-party extension
 }
 
 func (in *NodeExtensionStrategy) DeepCopyInto(out *NodeExtensionStrategy) {
diff --git a/pkg/koordlet/statesinformer/impl/states_nodeslo.go b/pkg/koordlet/statesinformer/impl/states_nodeslo.go
index dbdd9d291..1cb266146 100644
--- a/pkg/koordlet/statesinformer/impl/states_nodeslo.go
+++ b/pkg/koordlet/statesinformer/impl/states_nodeslo.go
@@ -254,11 +254,18 @@ func mergeSLOSpecExtensions(defaultSpec,
 	if newSpec != nil {
 		spec = newSpec
 	}
-	// ignore err for serializing/deserializing the same struct type
-	data, _ := json.Marshal(spec)
-	// NOTE: use deepcopy to avoid a overwrite to the global default
+
 	out := defaultSpec.DeepCopy()
-	_ = json.Unmarshal(data, &out)
+	for key := range out.Object {
+		// merge extension one by one so that all extension types can be protected during unmarshal
+		if newObj, exist := spec.Object[key]; exist {
+			// ignore err for serializing/deserializing the same struct type
+			data, _ := json.Marshal(newObj)
+			// NOTE: use deepcopy to avoid a overwrite to the global default
+			_ = json.Unmarshal(data, out.Object[key])
+		}
+	}
+
 	return out
 }
 
diff --git a/pkg/koordlet/statesinformer/impl/states_nodeslo_test.go b/pkg/koordlet/statesinformer/impl/states_nodeslo_test.go
index 855d5e8ad..50e22441b 100644
--- a/pkg/koordlet/statesinformer/impl/states_nodeslo_test.go
+++ b/pkg/koordlet/statesinformer/impl/states_nodeslo_test.go
@@ -58,7 +58,6 @@ func Test_mergeNodeSLOSpec(t *testing.T) {
 		SystemStrategy: &slov1alpha1.SystemStrategy{
 			WatermarkScaleFactor: pointer.Int64(200),
 		},
-		Extensions: &slov1alpha1.ExtensionsMap{},
 	}
 	testingMergedNodeSLOSpec := sloconfig.DefaultNodeSLOSpecConfig()
 	mergedInterface, err := util.MergeCfg(&testingMergedNodeSLOSpec, &testingCustomNodeSLOSpec)