diff --git a/src/compile/utils/scope.ts b/src/compile/utils/scope.ts
index 20cca46cba3e..6488986d83ae 100644
--- a/src/compile/utils/scope.ts
+++ b/src/compile/utils/scope.ts
@@ -75,12 +75,10 @@ export class Scope {
 		if (node.kind === 'var' && this.block && this.parent) {
 			this.parent.add_declaration(node);
 		} else if (node.type === 'VariableDeclaration') {
-			const initialised = !!node.init;
-
 			node.declarations.forEach((declarator: Node) => {
 				extract_names(declarator.id).forEach(name => {
 					this.declarations.set(name, node);
-					if (initialised) this.initialised_declarations.add(name);
+					if (declarator.init) this.initialised_declarations.add(name);
 				});
 			});
 		} else {
diff --git a/test/runtime/samples/dev-warning-missing-data-binding/main.svelte b/test/runtime/samples/dev-warning-missing-data-binding/main.svelte
index 3714351783f8..cfc7830c9048 100644
--- a/test/runtime/samples/dev-warning-missing-data-binding/main.svelte
+++ b/test/runtime/samples/dev-warning-missing-data-binding/main.svelte
@@ -1,5 +1,6 @@
 <script>
 	export let value;
+	export let value_with_default = undefined;
 </script>
 
 <input bind:value>
\ No newline at end of file
diff --git a/test/runtime/samples/dev-warning-missing-data-component/Foo.svelte b/test/runtime/samples/dev-warning-missing-data-component/Foo.svelte
index 95422444ccbe..99e26245ae3d 100644
--- a/test/runtime/samples/dev-warning-missing-data-component/Foo.svelte
+++ b/test/runtime/samples/dev-warning-missing-data-component/Foo.svelte
@@ -1,6 +1,7 @@
 <script>
 	export let x;
 	export let y;
+	export let z = undefined;
 </script>
 
 <div>{x} {y}</div>
\ No newline at end of file