diff --git a/packages/next-env/index.ts b/packages/next-env/index.ts
index a36abfc194a84..72a92282683fb 100644
--- a/packages/next-env/index.ts
+++ b/packages/next-env/index.ts
@@ -20,6 +20,18 @@ type Log = {
   error: (...args: any[]) => void
 }
 
+function replaceProcessEnv(sourceEnv: Env) {
+  Object.keys(process.env).forEach((key) => {
+    if (sourceEnv[key] === undefined || sourceEnv[key] === '') {
+      delete process.env[key]
+    }
+  })
+
+  Object.entries(sourceEnv).forEach(([key, value]) => {
+    process.env[key] = value
+  })
+}
+
 export function processEnv(
   loadedEnvFiles: LoadedEnvFiles,
   dir?: string,
@@ -94,7 +106,7 @@ export function loadEnvConfig(
   if (combinedEnv && !forceReload) {
     return { combinedEnv, loadedEnvFiles: cachedLoadedEnvFiles }
   }
-  process.env = Object.assign({}, initialEnv)
+  replaceProcessEnv(initialEnv)
   previousLoadedEnvFiles = cachedLoadedEnvFiles
   cachedLoadedEnvFiles = []
 
diff --git a/test/unit/preserve-process-env.test.ts b/test/unit/preserve-process-env.test.ts
new file mode 100644
index 0000000000000..cbddc233040e7
--- /dev/null
+++ b/test/unit/preserve-process-env.test.ts
@@ -0,0 +1,9 @@
+import { loadEnvConfig } from '../../packages/next-env/'
+
+describe('preserve process env', () => {
+  it('should not reassign `process.env`', () => {
+    const originalProcessEnv = process.env
+    loadEnvConfig('.')
+    expect(Object.is(originalProcessEnv, process.env)).toBeTrue()
+  })
+})