diff --git a/doc/qweb.md b/doc/qweb.md
index dce6b7f2..ea58143e 100644
--- a/doc/qweb.md
+++ b/doc/qweb.md
@@ -12,7 +12,8 @@
   - [`t-set` directive](#t-set-directive)
   - [`t-if` directive](#t-if-directive)
   - [Expression evaluation](#expression-evaluation)
-  - [`t-att` directive (dynamic attributes)](#t-att-directive-dynamic-attributes)
+  - [Dynamic attributes (`t-att` and `t-attf` directives)](#dynamic-attributes-t-att-and-t-attf-directives)
+  - [`t-attf` directive (dynamic attributes)](#t-att-directive-dynamic-attributes)
   - [`t-call` directive (sub templates)](#t-call-directive-sub-templates)
 
 - [JS/OWL Specific Extensions](#jsowl-specific-extensions)
@@ -257,7 +258,7 @@ compile time.
    <div><p t-if="10 + 2 gt 5">ok</p></div>
    ```
 
-### `t-att` directive (dynamic attributes)
+### Dynamic attributes (`t-att` and `t-attf` directives)
 
 One can use the `t-att-` directive to add dynamic attributes. Its main use is to
 evaluate an expression (at rendering time) and bind an attribute to its result:
@@ -265,7 +266,7 @@ evaluate an expression (at rendering time) and bind an attribute to its result:
 For example, if we have `id` set to 32 in the rendering context,
 
 ```xml
-<div t-att-data-action-id="id"/>  <!-- result: <div data-action-id="32"></div> -->
+<div t-att-data-action-id="id"/> <!-- result: <div data-action-id="32"></div> -->
 ```
 
 If an expression evaluates to a falsy value, it will not be set at all:
@@ -274,6 +275,21 @@ If an expression evaluates to a falsy value, it will not be set at all:
 <div t-att-foo="false"/>  <!-- result: <div></div> -->
 ```
 
+There is another way to format a string attribute: the `t-attf-` directive. With
+it, you get string interpolation:
+
+```xml
+<div t-attf-foo="a {{value1}} is {{value2}} of {{value3}} ]"/>
+<!-- result if values are set to 1,2 and 3: <div foo="a 0 is 1 of 2 ]"></div> -->
+```
+
+For historical reason, there is an alternate form of string interpolation:
+
+```xml
+<div t-attf-foo="a #{value1} is #{value2} of #{value3} ]"/>
+<!-- result if values are set to 1,2 and 3: <div foo="a 0 is 1 of 2 ]"></div> -->
+```
+
 ### `t-call` directive (sub templates)
 
 QWeb templates can be used for top level rendering, but they can also be used
diff --git a/src/qweb_core.ts b/src/qweb_core.ts
index 11d63fe4..a007a7ab 100644
--- a/src/qweb_core.ts
+++ b/src/qweb_core.ts
@@ -457,6 +457,9 @@ export class QWeb {
         props.push(`${key}: _${val}`);
       }
     }
+    function formatter(expr) {
+      return "${" + ctx.formatExpression(expr) + "}";
+    }
 
     for (let i = 0; i < attributes.length; i++) {
       let name = attributes[i].name;
@@ -515,10 +518,9 @@ export class QWeb {
           // attribute contains 'non letters' => we want to quote it
           attName = '"' + attName + '"';
         }
-        const formattedExpr = value!.replace(
-          /\{\{.*?\}\}/g,
-          s => "${" + ctx.formatExpression(s.slice(2, -2)) + "}"
-        );
+        const formattedExpr = value!
+          .replace(/\{\{.*?\}\}/g, s => formatter(s.slice(2, -2)))
+          .replace(/\#\{.*?\}/g, s => formatter(s.slice(2, -1)));
         const attID = ctx.generateID();
         let staticVal = (<Element>node).getAttribute(attName);
         if (staticVal) {
diff --git a/tests/__snapshots__/qweb.test.ts.snap b/tests/__snapshots__/qweb.test.ts.snap
index 3bb77670..92355c51 100644
--- a/tests/__snapshots__/qweb.test.ts.snap
+++ b/tests/__snapshots__/qweb.test.ts.snap
@@ -93,6 +93,17 @@ exports[`attributes format expression 1`] = `
 }"
 `;
 
+exports[`attributes format expression, other format 1`] = `
+"function anonymous(context,extra
+) {
+    var h = this.utils.h;
+    var _1 = \`\${context['value'] + 37}\`;
+    let c2 = [], p2 = {key:2,attrs:{foo: _1}};
+    var vn2 = h('div', p2, c2);
+    return vn2;
+}"
+`;
+
 exports[`attributes format literal 1`] = `
 "function anonymous(context,extra
 ) {
diff --git a/tests/qweb.test.ts b/tests/qweb.test.ts
index 3b3808a3..54446d93 100644
--- a/tests/qweb.test.ts
+++ b/tests/qweb.test.ts
@@ -511,6 +511,12 @@ describe("attributes", () => {
     expect(result).toBe(`<div foo="42"></div>`);
   });
 
+  test("format expression, other format", () => {
+    qweb.addTemplate("test", `<div t-attf-foo="#{value + 37}"/>`);
+    const result = renderToString(qweb, "test", { value: 5 });
+    expect(result).toBe(`<div foo="42"></div>`);
+  });
+
   test("format multiple", () => {
     qweb.addTemplate(
       "test",