diff --git a/packages/angular/cli/lib/config/schema.json b/packages/angular/cli/lib/config/schema.json
index a198aaa60e35..189b8e443cab 100644
--- a/packages/angular/cli/lib/config/schema.json
+++ b/packages/angular/cli/lib/config/schema.json
@@ -1234,6 +1234,7 @@
             },
             "optimization": {
               "description": "Enable optimization of the build output.",
+              "default": false,
               "oneOf": [
                 {
                   "type": "object",
@@ -1719,6 +1720,7 @@
             },
             "optimization": {
               "description": "Enables optimization of the build output.",
+              "default": false,
               "oneOf": [
                 {
                   "type": "object",