diff --git a/lib/core/src/server/__snapshots__/mergeConfigs.test.js.snap b/lib/core/src/server/__snapshots__/mergeConfigs.test.js.snap
index b3a99e4f2f6..c33eda68bd0 100644
--- a/lib/core/src/server/__snapshots__/mergeConfigs.test.js.snap
+++ b/lib/core/src/server/__snapshots__/mergeConfigs.test.js.snap
@@ -12,6 +12,12 @@ Object {
       "r2",
     ],
   },
+  "optimization": Object {
+    "runtimeChunk": true,
+    "splitChunks": Object {
+      "chunks": "all",
+    },
+  },
   "output": Object {
     "filename": "[name].js",
   },
@@ -48,6 +54,12 @@ Object {
       "r2",
     ],
   },
+  "optimization": Object {
+    "runtimeChunk": true,
+    "splitChunks": Object {
+      "chunks": "all",
+    },
+  },
   "output": Object {
     "filename": "[name].js",
   },
@@ -84,6 +96,15 @@ Object {
       "r4",
     ],
   },
+  "optimization": Object {
+    "minimizer": Array [
+      "banana",
+    ],
+    "runtimeChunk": true,
+    "splitChunks": Object {
+      "chunks": "all",
+    },
+  },
   "output": Object {
     "filename": "[name].js",
   },
diff --git a/lib/core/src/server/mergeConfigs.js b/lib/core/src/server/mergeConfigs.js
index 3bfa635d5b0..7b259cba86d 100644
--- a/lib/core/src/server/mergeConfigs.js
+++ b/lib/core/src/server/mergeConfigs.js
@@ -34,6 +34,16 @@ function resolve({ resolve: defaultResolve = {} }, { resolve: customResolve = {}
   };
 }
 
+function optimization(
+  { optimization: defaultOptimization = {} },
+  { optimization: customOptimization = {} }
+) {
+  return {
+    ...defaultOptimization,
+    ...customOptimization,
+  };
+}
+
 function mergeConfigs(config, customConfig) {
   return {
     // We'll always load our configurations after the custom config.
@@ -44,6 +54,7 @@ function mergeConfigs(config, customConfig) {
     plugins: plugins(config, customConfig),
     module: module(config, customConfig),
     resolve: resolve(config, customConfig),
+    optimization: optimization(config, customConfig),
   };
 }
 
diff --git a/lib/core/src/server/mergeConfigs.test.js b/lib/core/src/server/mergeConfigs.test.js
index 0d3d4cff8b2..da2962bcb8e 100644
--- a/lib/core/src/server/mergeConfigs.test.js
+++ b/lib/core/src/server/mergeConfigs.test.js
@@ -20,6 +20,12 @@ const config = {
       A2: 'src/B2',
     },
   },
+  optimization: {
+    splitChunks: {
+      chunks: 'all',
+    },
+    runtimeChunk: true,
+  },
 };
 
 describe('mergeConfigs', () => {
@@ -45,6 +51,9 @@ describe('mergeConfigs', () => {
           A4: 'src/B4',
         },
       },
+      optimization: {
+        minimizer: ['banana'],
+      },
     };
 
     const result = mergeConfigs(config, customConfig);