diff --git a/src/compile/Component.ts b/src/compile/Component.ts
index f2b6d25121..62c2931f62 100644
--- a/src/compile/Component.ts
+++ b/src/compile/Component.ts
@@ -1143,9 +1143,12 @@ export default class Component {
 		if (template_scope && template_scope.names.has(name)) return;
 		if (globalWhitelist.has(name)) return;
 
+		let message = `'${name}' is not defined`;
+		if (!this.ast.instance) message += `. Consider adding a <script> block with 'export let ${name}' to declare a prop`;
+
 		this.warn(node, {
 			code: 'missing-declaration',
-			message: `'${name}' is not defined`
+			message
 		});
 	}
 }
diff --git a/test/validator/samples/action-invalid/warnings.json b/test/validator/samples/action-invalid/warnings.json
index d5c38acf48..c1c1b2b492 100644
--- a/test/validator/samples/action-invalid/warnings.json
+++ b/test/validator/samples/action-invalid/warnings.json
@@ -1,6 +1,6 @@
 [{
 	"code": "missing-declaration",
-	"message": "'whatever' is not defined",
+	"message": "'whatever' is not defined. Consider adding a <script> block with 'export let whatever' to declare a prop",
 	"pos": 5,
 	"start": {
 		"line": 1,
diff --git a/test/validator/samples/missing-component/warnings.json b/test/validator/samples/missing-component/warnings.json
index 6aed92a6ad..9c95cd81f1 100644
--- a/test/validator/samples/missing-component/warnings.json
+++ b/test/validator/samples/missing-component/warnings.json
@@ -1,6 +1,6 @@
 [{
 	"code": "missing-declaration",
-	"message": "'Widget' is not defined",
+	"message": "'Widget' is not defined. Consider adding a <script> block with 'export let Widget' to declare a prop",
 	"start": {
 		"line": 2,
 		"column": 1,
diff --git a/test/validator/samples/transition-missing/warnings.json b/test/validator/samples/transition-missing/warnings.json
index b50d55d579..19520a6729 100644
--- a/test/validator/samples/transition-missing/warnings.json
+++ b/test/validator/samples/transition-missing/warnings.json
@@ -1,6 +1,6 @@
 [{
 	"code": "missing-declaration",
-	"message": "'foo' is not defined",
+	"message": "'foo' is not defined. Consider adding a <script> block with 'export let foo' to declare a prop",
 	"start": {
 		"line": 1,
 		"column": 5,