diff --git a/.changeset/great-geckos-marry.md b/.changeset/great-geckos-marry.md
new file mode 100644
index 000000000..4e6cfdf3e
--- /dev/null
+++ b/.changeset/great-geckos-marry.md
@@ -0,0 +1,5 @@
+---
+'@vanilla-extract/vite-plugin': patch
+---
+
+Prevent unnecessary module invalidations when using PostCSS
diff --git a/packages/vite-plugin/src/index.ts b/packages/vite-plugin/src/index.ts
index 0bc3076d1..6a807fc2d 100644
--- a/packages/vite-plugin/src/index.ts
+++ b/packages/vite-plugin/src/index.ts
@@ -214,7 +214,7 @@ export function vanillaExtractPlugin({
           if (
             server &&
             cssMap.has(absoluteId) &&
-            cssMap.get(absoluteId) !== source
+            cssMap.get(absoluteId) !== cssSource
           ) {
             const { moduleGraph } = server;
             const modules = Array.from(