diff --git a/packages/next/build/webpack/loaders/next-flight-css-dev-loader.ts b/packages/next/build/webpack/loaders/next-flight-css-dev-loader.ts
index 8bfd62b9f38f189..43f994e35b423b7 100644
--- a/packages/next/build/webpack/loaders/next-flight-css-dev-loader.ts
+++ b/packages/next/build/webpack/loaders/next-flight-css-dev-loader.ts
@@ -5,25 +5,32 @@
  */
 
 export function pitch(this: any) {
-  const content = this.fs.readFileSync(this.resourcePath)
-  this.data.__checksum = (
-    typeof content === 'string' ? Buffer.from(content) : content
-  ).toString('hex')
+  if (process.env.NODE_ENV !== 'production') {
+    const content = this.fs.readFileSync(this.resourcePath)
+    this.data.__checksum = (
+      typeof content === 'string' ? Buffer.from(content) : content
+    ).toString('hex')
+  }
 }
 
 const NextServerCSSLoader = function (this: any, content: string) {
   this.cacheable && this.cacheable()
 
-  const isCSSModule = this.resourcePath.match(/\.module\.(css|sass|scss)$/)
-  if (isCSSModule) {
-    return (
-      content +
-      '\nmodule.exports.__checksum = ' +
-      JSON.stringify(this.data.__checksum)
-    )
+  // Only add the checksum during development.
+  if (process.env.NODE_ENV !== 'production') {
+    const isCSSModule = this.resourcePath.match(/\.module\.(css|sass|scss)$/)
+    if (isCSSModule) {
+      return (
+        content +
+        '\nmodule.exports.__checksum = ' +
+        JSON.stringify(this.data.__checksum)
+      )
+    }
+
+    return `export default ${JSON.stringify(this.data.__checksum)}`
   }
 
-  return `export default ${JSON.stringify(this.data.__checksum)}`
+  return content
 }
 
 export default NextServerCSSLoader