diff --git a/crates/mako/src/build/transform.rs b/crates/mako/src/build/transform.rs
index 542221b11..4249509bc 100644
--- a/crates/mako/src/build/transform.rs
+++ b/crates/mako/src/build/transform.rs
@@ -235,16 +235,10 @@ impl Context {
         let is_ts = file.extname == "ts" || file.extname == "tsx";
 
         let mut assumptions = Assumptions::default();
-        self.config.js.as_ref().map(|js_config| {
-            js_config.transform.as_ref().map(|transform_config| {
-                assumptions.set_public_class_fields |=
-                    !transform_config.use_define_for_class_fields;
-                if is_ts {
-                    assumptions.set_class_methods |= !transform_config.use_define_for_class_fields;
-                }
-            })
-        });
-
+        assumptions.set_public_class_fields |= !self.config.use_define_for_class_fields;
+        if is_ts {
+            assumptions.set_class_methods |= !self.config.use_define_for_class_fields;
+        }
         assumptions
     }
 }
diff --git a/crates/mako/src/config/config.rs b/crates/mako/src/config/config.rs
index 449c92a51..dc9dfbf4a 100644
--- a/crates/mako/src/config/config.rs
+++ b/crates/mako/src/config/config.rs
@@ -478,7 +478,7 @@ pub struct Config {
     pub rsc_client: Option<RscClientConfig>,
     pub experimental: ExperimentalConfig,
     pub watch: WatchConfig,
-    pub js: Option<JsConfig>,
+    pub use_define_for_class_fields: bool,
 }
 
 #[allow(dead_code)]
@@ -527,34 +527,6 @@ pub struct OptimizeChunkGroup {
     #[serde(default, with = "optimize_test_format")]
     pub test: Option<Regex>,
 }
-#[derive(Deserialize, Serialize, Clone, Debug)]
-#[serde(rename_all = "camelCase")]
-pub struct JsConfig {
-    pub transform: Option<TransformConfig>,
-}
-
-impl Default for JsConfig {
-    fn default() -> Self {
-        JsConfig {
-            transform: Some(TransformConfig::default()),
-        }
-    }
-}
-
-#[derive(Deserialize, Serialize, Clone, Debug)]
-#[serde(rename_all = "camelCase")]
-pub struct TransformConfig {
-    #[serde(default)]
-    pub use_define_for_class_fields: bool,
-}
-
-impl Default for TransformConfig {
-    fn default() -> Self {
-        TransformConfig {
-            use_define_for_class_fields: true,
-        }
-    }
-}
 
 impl Default for OptimizeChunkGroup {
     fn default() -> Self {
@@ -661,9 +633,7 @@ const DEFAULT_CONFIG: &str = r#"
     "rscServer": false,
     "rscClient": false,
     "experimental": { "webpackSyntaxValidate": [] },
-    "js": {
-      "useDefineForClassFields": true
-    },
+    "useDefineForClassFields": true,
     "watch": { "ignorePaths": [] }
 }
 "#;