diff --git a/src/compiler/preprocess/index.ts b/src/compiler/preprocess/index.ts
index 0b83c05deb..60609f0275 100644
--- a/src/compiler/preprocess/index.ts
+++ b/src/compiler/preprocess/index.ts
@@ -184,19 +184,25 @@ export default async function preprocess(
 		if (p.markup) {
 			processed = await process_markup(source, p.markup, filename);
 			source = processed.source;
-			if (processed.dependencies.length) dependencies.push(...processed.dependencies);
+			if (processed.dependencies && processed.dependencies.length) {
+				dependencies.push(...processed.dependencies);
+			}
 		}
 
 		if (p.script) {
 			processed = await process_script(source, p.script, filename);
 			source = processed.source;
-			if (processed.dependencies.length) dependencies.push(...processed.dependencies);
+			if (processed.dependencies && processed.dependencies.length) {
+				dependencies.push(...processed.dependencies);
+			}
 		}
 
 		if (p.style) {
 			processed = await process_style(source, p.style, filename);
 			source = processed.source;
-			if (processed.dependencies.length) dependencies.push(...processed.dependencies);
+			if (processed.dependencies && processed.dependencies.length) {
+				dependencies.push(...processed.dependencies);
+			}
 		}
 	});
 
diff --git a/test/preprocess/samples/strict-order/_config.js b/test/preprocess/samples/strict-order/_config.js
new file mode 100644
index 0000000000..e47e14b929
--- /dev/null
+++ b/test/preprocess/samples/strict-order/_config.js
@@ -0,0 +1,11 @@
+export default {
+	strictOrder: false,
+	preprocess: [
+		{
+			style: ({ content }) => ({ code: content.replace(/one/g, 'two') }),
+		},
+		{
+			markup: ({ content }) => ({ code: content.replace(/two/g, 'three') }),
+		},
+	],
+};
diff --git a/test/preprocess/samples/strict-order/input.svelte b/test/preprocess/samples/strict-order/input.svelte
new file mode 100644
index 0000000000..3bf89c6b95
--- /dev/null
+++ b/test/preprocess/samples/strict-order/input.svelte
@@ -0,0 +1,11 @@
+<p>one</p>
+
+<style>
+	.three {
+		color: red;
+	}
+</style>
+
+<script>
+	console.log('one');
+</script>
\ No newline at end of file
diff --git a/test/preprocess/samples/strict-order/output.svelte b/test/preprocess/samples/strict-order/output.svelte
new file mode 100644
index 0000000000..3bf89c6b95
--- /dev/null
+++ b/test/preprocess/samples/strict-order/output.svelte
@@ -0,0 +1,11 @@
+<p>one</p>
+
+<style>
+	.three {
+		color: red;
+	}
+</style>
+
+<script>
+	console.log('one');
+</script>
\ No newline at end of file