diff --git a/src/compiler/compile/render_dom/Renderer.ts b/src/compiler/compile/render_dom/Renderer.ts
index 29389ed3c3d8..035b47e74f7c 100644
--- a/src/compiler/compile/render_dom/Renderer.ts
+++ b/src/compiler/compile/render_dom/Renderer.ts
@@ -220,7 +220,11 @@ export default class Renderer {
 				const i = (value / 31) | 0;
 				const n = 1 << (value % 31);
 
-				if (!bitmask[i]) bitmask[i] = { n: 0, names: [] };
+				if (bitmask.length <= i) {
+					for (let j = bitmask.length; j <= i; j++) {
+						bitmask[j] = { n: 0, names: [] };
+					}
+				}
 
 				bitmask[i].n |= n;
 				bitmask[i].names.push(name);
diff --git a/test/runtime/samples/bitmask-overflow-3/_config.js b/test/runtime/samples/bitmask-overflow-3/_config.js
new file mode 100644
index 000000000000..13f18b386cb2
--- /dev/null
+++ b/test/runtime/samples/bitmask-overflow-3/_config.js
@@ -0,0 +1,4 @@
+export default {
+	solo: true,
+	error: `A is not defined`,
+};
\ No newline at end of file
diff --git a/test/runtime/samples/bitmask-overflow-3/main.svelte b/test/runtime/samples/bitmask-overflow-3/main.svelte
new file mode 100644
index 000000000000..aa2c56a14759
--- /dev/null
+++ b/test/runtime/samples/bitmask-overflow-3/main.svelte
@@ -0,0 +1,4 @@
+<script>
+	let x1, x2, x3, x4, x5, x6, x7, x8, x9, x10, x11, x12, x13, x14, x15, x16, x17, x18, x19, x20, x21, x22, x23, x24, x25, x26, x27, x28, x29, x30, x31;
+</script>
+<A>foo</A>