diff --git a/public/app/features/dashboard-scene/settings/variables/components/QueryVariableForm.tsx b/public/app/features/dashboard-scene/settings/variables/components/QueryVariableForm.tsx
index d6d4d467c9a..3849fb0a2c5 100644
--- a/public/app/features/dashboard-scene/settings/variables/components/QueryVariableForm.tsx
+++ b/public/app/features/dashboard-scene/settings/variables/components/QueryVariableForm.tsx
@@ -89,6 +89,14 @@ export function QueryVariableEditorForm({
       onQueryChange(query);
     }
 
+    if (!datasourceRef) {
+      const instanceSettings = getDataSourceSrv().getInstanceSettings({ type: datasource.type, uid: datasource.uid });
+
+      if (instanceSettings) {
+        onDataSourceChange(instanceSettings);
+      }
+    }
+
     return { datasource, VariableQueryEditor };
   }, [datasourceRef]);
 
diff --git a/public/app/features/dashboard-scene/settings/variables/editors/QueryVariableEditor.test.tsx b/public/app/features/dashboard-scene/settings/variables/editors/QueryVariableEditor.test.tsx
index ff1b0e88a66..5b6579dcfa0 100644
--- a/public/app/features/dashboard-scene/settings/variables/editors/QueryVariableEditor.test.tsx
+++ b/public/app/features/dashboard-scene/settings/variables/editors/QueryVariableEditor.test.tsx
@@ -148,6 +148,20 @@ describe('QueryVariableEditor', () => {
     expect(staticOptionsToggle).toBeInTheDocument();
   });
 
+  it('should update the variable with default datasource when opening editor', async () => {
+    const onRunQueryMock = jest.fn();
+    const variable = new QueryVariable({ datasource: undefined, query: '' });
+
+    await setup({
+      variable,
+      onRunQuery: onRunQueryMock,
+    });
+
+    await waitFor(async () => {
+      expect(variable.state.datasource).not.toBe(undefined);
+    });
+  });
+
   it('should update the variable with default query for the selected DS', async () => {
     const onRunQueryMock = jest.fn();
     const variable = new QueryVariable({ datasource: { uid: 'mock-ds-2', type: 'test' }, query: '' });
diff --git a/public/app/features/variables/query/QueryVariableEditor.test.tsx b/public/app/features/variables/query/QueryVariableEditor.test.tsx
index 0322a73b048..44b2d98a0f9 100644
--- a/public/app/features/variables/query/QueryVariableEditor.test.tsx
+++ b/public/app/features/variables/query/QueryVariableEditor.test.tsx
@@ -29,7 +29,12 @@ ds.variables = {
 };
 
 const setupTestContext = async (options: Partial<Props>) => {
-  const variableDefaults: Partial<QueryVariableModel> = { rootStateKey: 'key' };
+  const variableDefaults: Partial<QueryVariableModel> = {
+    rootStateKey: 'key',
+    // adds a default datasource in old arch tests so they continue passing
+    // in new scenes arch the datasource will be calculated if not provided
+    datasource: { uid: 'uid', type: 'type' },
+  };
   const extended = {
     VariableQueryEditor: LegacyVariableQueryEditor,
     dataSource: ds,