diff --git a/src/preprocess.js b/src/preprocess.js
index 0fdc7cc..0be4795 100644
--- a/src/preprocess.js
+++ b/src/preprocess.js
@@ -172,6 +172,9 @@ export const preprocess = text => {
 				} else if (node.type === 'Element' || node.type === 'InlineComponent' || node.type === 'SlotTemplate') {
 					node.attributes.forEach(node => node.type === 'Let' && find_contextual_names(compiler, node.expression || node.name));
 				}
+				if (Array.isArray(node.children)) {
+					node.children.forEach(node => node.type === 'ConstTag' && find_contextual_names(compiler, node.expression.left.name));
+				}
 				if (contextual_names.length) {
 					nodes_with_contextual_scope.add(node);
 					block.transformed_code += `{let ${contextual_names.map(name => `${name}=0`).join(',')};`;
diff --git a/test/samples/const-tag/.eslintrc.js b/test/samples/const-tag/.eslintrc.js
new file mode 100644
index 0000000..1b241b7
--- /dev/null
+++ b/test/samples/const-tag/.eslintrc.js
@@ -0,0 +1,8 @@
+module.exports = {
+	rules: {
+		'no-undef': 'error',
+	},
+	settings: {
+		'svelte3/ignore-warnings': ({ code }) => code === 'missing-declaration',
+	},
+};
diff --git a/test/samples/const-tag/Input.svelte b/test/samples/const-tag/Input.svelte
new file mode 100644
index 0000000..8255686
--- /dev/null
+++ b/test/samples/const-tag/Input.svelte
@@ -0,0 +1,37 @@
+<script>
+	export let boxes;
+	let p;
+</script>
+
+{#each boxes as box}
+	{@const area = box.width * box.height}
+	{box.width} * {box.height} = {area}
+{/each}
+
+{area} <!-- undef -->
+
+{#await p}
+	wait
+{:then}
+	{@const box = boxes[0]}
+	{box.width}
+{/await}
+
+{#await p then}
+	then
+{:catch}
+	{@const box = boxes[0]}
+	{box.width}
+{/await}
+
+<Component>
+	{@const box = boxes[0]}
+	{box.width}
+</Component>
+
+<Component>
+	<svelte:fragment slot="foo">
+		{@const box = boxes[0]}
+		{box.width}
+	</svelte:fragment>
+</Component>
diff --git a/test/samples/const-tag/expected.json b/test/samples/const-tag/expected.json
new file mode 100644
index 0000000..7bd208f
--- /dev/null
+++ b/test/samples/const-tag/expected.json
@@ -0,0 +1,9 @@
+[
+	{
+		"ruleId": "no-undef",
+		"line": 11,
+		"column": 2,
+		"endLine": 11,
+		"endColumn": 6
+	}
+]