diff --git a/public/app/features/dashboard-scene/serialization/sceneVariablesSetToVariables.ts b/public/app/features/dashboard-scene/serialization/sceneVariablesSetToVariables.ts
index 4fad1e3b317..fe7b56e22b5 100644
--- a/public/app/features/dashboard-scene/serialization/sceneVariablesSetToVariables.ts
+++ b/public/app/features/dashboard-scene/serialization/sceneVariablesSetToVariables.ts
@@ -554,7 +554,7 @@ export function sceneVariablesSetToSchemaV2Variables(
             ...validateFiltersOrigin(variable.state.originFilters),
             ...validateFiltersOrigin(variable.state.filters),
           ],
-          defaultKeys: variable.state.defaultKeys || [], //FIXME what is the default value?
+          defaultKeys: variable.state.defaultKeys || [],
           allowCustomValue: variable.state.allowCustomValue ?? true,
         },
       };
diff --git a/public/app/features/dashboard-scene/serialization/testfiles/nested_dashboard.json b/public/app/features/dashboard-scene/serialization/testfiles/nested_dashboard.json
index 4322333ceb1..8a39daf6155 100644
--- a/public/app/features/dashboard-scene/serialization/testfiles/nested_dashboard.json
+++ b/public/app/features/dashboard-scene/serialization/testfiles/nested_dashboard.json
@@ -1137,7 +1137,13 @@
       "datasource": { "name": "esmce00tbim8" },
       "group": "opensearch",
       "spec": {
-        "allowCustomValue": true
+        "name": "adhocVar",
+        "allowCustomValue": true,
+        "filters": [],
+        "baseFilters": [],
+        "defaultKeys": [],
+        "hide": "dontHide",
+        "skipUrlSync": false
       }
     },
     {
diff --git a/public/app/features/dashboard-scene/serialization/transformSaveModelSchemaV2ToScene.test.ts b/public/app/features/dashboard-scene/serialization/transformSaveModelSchemaV2ToScene.test.ts
index f054a9f7cab..aae2599b906 100644
--- a/public/app/features/dashboard-scene/serialization/transformSaveModelSchemaV2ToScene.test.ts
+++ b/public/app/features/dashboard-scene/serialization/transformSaveModelSchemaV2ToScene.test.ts
@@ -365,6 +365,35 @@ describe('transformSaveModelSchemaV2ToScene', () => {
     expect(getQueryRunnerFor(vizPanels[0])?.state.datasource?.uid).toBe(MIXED_DATASOURCE_NAME);
   });
 
+  describe('adhoc variables', () => {
+    it('should convert empty defaultKeys array to undefined', () => {
+      const dashboard = cloneDeep(defaultDashboard);
+      const adhocVar = dashboard.spec.variables.find((v) => v.kind === 'AdhocVariable') as AdhocVariableKind;
+      adhocVar.spec.defaultKeys = [];
+
+      const scene = transformSaveModelSchemaV2ToScene(dashboard);
+
+      const adhocVariable = scene.state.$variables?.getByName('adhocVar') as AdHocFiltersVariable;
+      expect(adhocVariable).toBeInstanceOf(AdHocFiltersVariable);
+
+      expect(adhocVariable.state.defaultKeys).toBeUndefined();
+    });
+
+    it('should preserve non-empty defaultKeys array', () => {
+      const dashboard = cloneDeep(defaultDashboard);
+
+      const adhocVar = dashboard.spec.variables.find((v) => v.kind === 'AdhocVariable') as AdhocVariableKind;
+      expect(adhocVar.spec.defaultKeys.length).toBeGreaterThan(0);
+
+      const scene = transformSaveModelSchemaV2ToScene(dashboard);
+
+      const adhocVariable = scene.state.$variables?.getByName('adhocVar') as AdHocFiltersVariable;
+      expect(adhocVariable).toBeInstanceOf(AdHocFiltersVariable);
+
+      expect(adhocVariable.state.defaultKeys).toEqual(adhocVar.spec.defaultKeys);
+    });
+  });
+
   describe('When creating a snapshot dashboard scene', () => {
     it('should initialize a dashboard scene with SnapshotVariables', () => {
       const snapshot: DashboardWithAccessInfo<DashboardV2Spec> = {
@@ -401,6 +430,29 @@ describe('transformSaveModelSchemaV2ToScene', () => {
       expect(intervalSnapshot.state.text).toBe('1m');
       expect(intervalSnapshot.state.isReadOnly).toBe(true);
     });
+
+    it('should convert empty defaultKeys array to undefined for adhoc variables', () => {
+      const snapshot: DashboardWithAccessInfo<DashboardV2Spec> = cloneDeep({
+        ...defaultDashboard,
+        metadata: {
+          ...defaultDashboard.metadata,
+          annotations: {
+            ...defaultDashboard.metadata.annotations,
+            [AnnoKeyDashboardIsSnapshot]: 'true',
+          },
+        },
+      });
+
+      const adhocVar = snapshot.spec.variables.find((v) => v.kind === 'AdhocVariable') as AdhocVariableKind;
+      adhocVar.spec.defaultKeys = [];
+
+      const scene = transformSaveModelSchemaV2ToScene(snapshot);
+
+      const adhocVariable = scene.state.$variables?.getByName('adhocVar') as AdHocFiltersVariable;
+      expect(adhocVariable).toBeInstanceOf(AdHocFiltersVariable);
+
+      expect(adhocVariable.state.defaultKeys).toBeUndefined();
+    });
   });
 
   describe('meta', () => {
diff --git a/public/app/features/dashboard-scene/serialization/transformSaveModelSchemaV2ToScene.ts b/public/app/features/dashboard-scene/serialization/transformSaveModelSchemaV2ToScene.ts
index 09cae3ef7da..ff3927d3814 100644
--- a/public/app/features/dashboard-scene/serialization/transformSaveModelSchemaV2ToScene.ts
+++ b/public/app/features/dashboard-scene/serialization/transformSaveModelSchemaV2ToScene.ts
@@ -329,7 +329,7 @@ function createSceneVariableFromVariableModel(variable: TypedVariableModelV2): S
       applyMode: 'auto',
       filters: variable.spec.filters ?? [],
       baseFilters: variable.spec.baseFilters ?? [],
-      defaultKeys: variable.spec.defaultKeys,
+      defaultKeys: variable.spec.defaultKeys.length ? variable.spec.defaultKeys : undefined,
       useQueriesAsFilterForOptions: true,
       drilldownRecommendationsEnabled: config.featureToggles.drilldownRecommendations,
       layout: config.featureToggles.newFiltersUI ? 'combobox' : undefined,
@@ -538,7 +538,7 @@ export function createVariablesForSnapshot(dashboard: DashboardV2Spec): SceneVar
             applyMode: 'auto',
             filters: v.spec.filters ?? [],
             baseFilters: v.spec.baseFilters ?? [],
-            defaultKeys: v.spec.defaultKeys,
+            defaultKeys: v.spec.defaultKeys?.length ? v.spec.defaultKeys : undefined,
             useQueriesAsFilterForOptions: true,
             layout: config.featureToggles.newFiltersUI ? 'combobox' : undefined,
             supportsMultiValueOperators: Boolean(