diff --git a/web/static/src/ts/core/qweb_vdom.ts b/web/static/src/ts/core/qweb_vdom.ts
index af1eda93..a591f309 100644
--- a/web/static/src/ts/core/qweb_vdom.ts
+++ b/web/static/src/ts/core/qweb_vdom.ts
@@ -381,7 +381,7 @@ export class QWeb {
       // dynamic attributes
       if (name.startsWith("t-att-")) {
         const attName = name.slice(6);
-        const formattedValue = this._formatExpression(value!);
+        const formattedValue = this._formatExpression(ctx.getValue(value!));
         const attID = ctx.generateID();
         ctx.addLine(`let _${attID} = ${formattedValue};`);
         attrs.push(`${attName}: _${attID}`);
diff --git a/web/static/tests/core/__snapshots__/qweb_vdom.test.ts.snap b/web/static/tests/core/__snapshots__/qweb_vdom.test.ts.snap
index ea201244..9dd17fbb 100644
--- a/web/static/tests/core/__snapshots__/qweb_vdom.test.ts.snap
+++ b/web/static/tests/core/__snapshots__/qweb_vdom.test.ts.snap
@@ -77,6 +77,20 @@ exports[`attributes format value 1`] = `
 }"
 `;
 
+exports[`attributes from variables set previously 1`] = `
+"function anonymous(context,extra
+) {
+    let h = this.h;
+    let c1 = [], p1 = {};
+    let vn1 = h('div', p1, c1);
+    let _2 = 'def';
+    let c3 = [], p3 = {attrs:{class: _2}};
+    let vn3 = h('span', p3, c3);
+    c1.push(vn3);
+    return vn1;
+}"
+`;
+
 exports[`attributes object 1`] = `
 "function anonymous(context,extra
 ) {
diff --git a/web/static/tests/core/qweb_vdom.test.ts b/web/static/tests/core/qweb_vdom.test.ts
index 1982a8a5..e20dac5f 100644
--- a/web/static/tests/core/qweb_vdom.test.ts
+++ b/web/static/tests/core/qweb_vdom.test.ts
@@ -353,6 +353,28 @@ describe("attributes", () => {
     expect(result).toBe(`<div foo="bar"></div>`);
   });
 
+  test("from variables set previously", () => {
+    qweb.addTemplate(
+      "test",
+      `<div><t t-set="abc" t-value="'def'"/><span t-att-class="abc"/></div>`
+    );
+    const result = renderToString(qweb, "test");
+    expect(result).toBe('<div><span class="def"></span></div>');
+  });
+
+  test.skip("from object variables set previously", () => {
+    // qweb is stupid and does not support this.
+    // To do that properly, we need to extend the formatExpression method to
+    // be able to deal with objects.  I think that it is not easy:
+    // it should properly deal with stuff like {a:expr, b: {c: otherexpr}}
+    qweb.addTemplate(
+      "test",
+      `<div t-debug="1"><t t-set="o" t-value="{a:'b'}"/><span t-att-class="o.a"/></div>`
+    );
+    const result = renderToString(qweb, "test");
+    expect(result).toBe('<div><span class="b"></span></div>');
+  });
+
   test("format expression", () => {
     qweb.addTemplate("test", `<div t-attf-foo="{{value + 37}}"/>`);
     const result = renderToString(qweb, "test", { value: 5 });