diff --git a/src/compile/Component.ts b/src/compile/Component.ts
index f8ee5a0b78..21f0b6ef05 100644
--- a/src/compile/Component.ts
+++ b/src/compile/Component.ts
@@ -1182,7 +1182,7 @@ export default class Component {
 			if (name[0] === '$') return; // $$props
 		}
 
-		if (this.var_lookup.has(name)) return;
+		if (this.var_lookup.has(name) && !this.var_lookup.get(name).global) return;
 		if (template_scope && template_scope.names.has(name)) return;
 		if (globals.has(name)) return;
 
diff --git a/test/validator/samples/undefined-value-global/input.svelte b/test/validator/samples/undefined-value-global/input.svelte
new file mode 100644
index 0000000000..44e7332bf5
--- /dev/null
+++ b/test/validator/samples/undefined-value-global/input.svelte
@@ -0,0 +1,5 @@
+<script>
+	console.log(potato);
+</script>
+
+<p>{potato}</p>
diff --git a/test/validator/samples/undefined-value-global/warnings.json b/test/validator/samples/undefined-value-global/warnings.json
new file mode 100644
index 0000000000..ee9e3d6c90
--- /dev/null
+++ b/test/validator/samples/undefined-value-global/warnings.json
@@ -0,0 +1,15 @@
+[{
+	"code": "missing-declaration",
+	"message": "'potato' is not defined",
+	"pos": 46,
+	"start": {
+		"line": 5,
+		"column": 4,
+		"character": 46
+	},
+	"end": {
+		"line": 5,
+		"column": 10,
+		"character": 52
+	}
+}]