diff --git a/src/qweb_extensions.ts b/src/qweb_extensions.ts
index fbb30303..37c2f503 100644
--- a/src/qweb_extensions.ts
+++ b/src/qweb_extensions.ts
@@ -235,9 +235,11 @@ QWeb.addDirective({
       `def${defID} = w${widgetID}._updateProps(props${widgetID}, extra.forceUpdate, extra.patchQueue);`
     );
     ctx.addElse();
-    ctx.addLine(
-      `w${widgetID} = new context.widgets['${value}'](owner, props${widgetID});`
-    );
+    ctx.addLine(`let W${widgetID} = context.widgets['${value}'];`);
+
+    // maybe only do this in dev mode...
+    ctx.addLine(`if (!W${widgetID}) {throw new Error(\`Cannot find the definition of widget "${value}"\`)}`);
+    ctx.addLine(`w${widgetID} = new W${widgetID}(owner, props${widgetID});`);
     ctx.addLine(
       `context.__owl__.cmap[${templateID}] = w${widgetID}.__owl__.id;`
     );
diff --git a/tests/__snapshots__/component.test.ts.snap b/tests/__snapshots__/component.test.ts.snap
index 31005986..66c6ba27 100644
--- a/tests/__snapshots__/component.test.ts.snap
+++ b/tests/__snapshots__/component.test.ts.snap
@@ -31,7 +31,9 @@ exports[`class and style attributes with t-widget dynamic t-att-style is properl
         if (w4) {
             def3 = w4._updateProps(props4, extra.forceUpdate, extra.patchQueue);
         } else {
-            w4 = new context.widgets['child'](owner, props4);
+            let W4 = context.widgets['child'];
+            if (!W4) {throw new Error(\`Cannot find the definition of widget \\"child\\"\`)}
+            w4 = new W4(owner, props4);
             context.__owl__.cmap[4] = w4.__owl__.id;
             def3 = w4._prepare();
         }
@@ -78,7 +80,9 @@ exports[`class and style attributes with t-widget t-att-class is properly added/
         if (w4) {
             def3 = w4._updateProps(props4, extra.forceUpdate, extra.patchQueue);
         } else {
-            w4 = new context.widgets['child'](owner, props4);
+            let W4 = context.widgets['child'];
+            if (!W4) {throw new Error(\`Cannot find the definition of widget \\"child\\"\`)}
+            w4 = new W4(owner, props4);
             context.__owl__.cmap[4] = w4.__owl__.id;
             def3 = w4._prepare();
         }
@@ -143,7 +147,9 @@ exports[`composition sub widgets with some state rendered in a loop 1`] = `
             if (w7) {
                 def6 = w7._updateProps(props7, extra.forceUpdate, extra.patchQueue);
             } else {
-                w7 = new context.widgets['ChildWidget'](owner, props7);
+                let W7 = context.widgets['ChildWidget'];
+                if (!W7) {throw new Error(\`Cannot find the definition of widget \\"ChildWidget\\"\`)}
+                w7 = new W7(owner, props7);
                 context.__owl__.cmap[key8] = w7.__owl__.id;
                 def6 = w7._prepare();
             }
@@ -191,7 +197,9 @@ exports[`random stuff/miscellaneous snapshotting compiled code 1`] = `
         if (w4) {
             def3 = w4._updateProps(props4, extra.forceUpdate, extra.patchQueue);
         } else {
-            w4 = new context.widgets['child'](owner, props4);
+            let W4 = context.widgets['child'];
+            if (!W4) {throw new Error(\`Cannot find the definition of widget \\"child\\"\`)}
+            w4 = new W4(owner, props4);
             context.__owl__.cmap[key5] = w4.__owl__.id;
             def3 = w4._prepare();
         }
@@ -237,7 +245,9 @@ exports[`random stuff/miscellaneous t-props should not be undefined (snapshottin
         if (w4) {
             def3 = w4._updateProps(props4, extra.forceUpdate, extra.patchQueue);
         } else {
-            w4 = new context.widgets['child'](owner, props4);
+            let W4 = context.widgets['child'];
+            if (!W4) {throw new Error(\`Cannot find the definition of widget \\"child\\"\`)}
+            w4 = new W4(owner, props4);
             context.__owl__.cmap[4] = w4.__owl__.id;
             def3 = w4._prepare();
         }
diff --git a/tests/component.test.ts b/tests/component.test.ts
index cabb4713..fcb1c556 100644
--- a/tests/component.test.ts
+++ b/tests/component.test.ts
@@ -852,6 +852,25 @@ describe("composition", () => {
     expect(children(widget)[0].__owl__.parent).toBe(widget);
   });
 
+  test("throw a nice error if it cannot find widget", async () => {
+    expect.assertions(1);
+    env.qweb.addTemplate(
+      "Parent",
+      `<div><t t-widget="SomeMispelledWidget"/></div>`
+    );
+    class Parent extends Widget {
+      widgets = { SomeWidget: Widget };
+    }
+    const parent = new Parent(env);
+    try {
+      await parent.mount(fixture);
+    } catch (e) {
+      expect(e.message).toBe(
+        'Cannot find the definition of widget "SomeMispelledWidget"'
+      );
+    }
+  });
+
   test("t-refs on widget are widgets", async () => {
     env.qweb.addTemplate(
       "WidgetC",
@@ -1956,7 +1975,9 @@ describe("async rendering", () => {
 
     const app = new App(env);
     await app.mount(fixture);
-    expect(fixture.innerHTML).toBe("<div><ul><li><div>1</div></li><li><div>2</div></li></ul></div>");
+    expect(fixture.innerHTML).toBe(
+      "<div><ul><li><div>1</div></li><li><div>2</div></li></ul></div>"
+    );
   });
 
   test("properly behave when destroyed/unmounted while rendering ", async () => {