diff --git a/crates/node_binding/binding.d.ts b/crates/node_binding/binding.d.ts
index 31a5d915dcd1..1701083285a6 100644
--- a/crates/node_binding/binding.d.ts
+++ b/crates/node_binding/binding.d.ts
@@ -772,7 +772,7 @@ export interface RawCssAutoGeneratorOptions {
   exportsConvention?: "as-is" | "camel-case" | "camel-case-only" | "dashes" | "dashes-only"
   exportsOnly?: boolean
   localIdentName?: string
-  esModule: boolean
+  esModule?: boolean
 }
 
 export interface RawCssAutoParserOptions {
@@ -793,14 +793,14 @@ export interface RawCssExtractPluginOption {
 export interface RawCssGeneratorOptions {
   exportsConvention?: "as-is" | "camel-case" | "camel-case-only" | "dashes" | "dashes-only"
   exportsOnly?: boolean
-  esModule: boolean
+  esModule?: boolean
 }
 
 export interface RawCssModuleGeneratorOptions {
   exportsConvention?: "as-is" | "camel-case" | "camel-case-only" | "dashes" | "dashes-only"
   exportsOnly?: boolean
   localIdentName?: string
-  esModule: boolean
+  esModule?: boolean
 }
 
 export interface RawCssModuleParserOptions {
diff --git a/crates/rspack_binding_options/src/options/raw_module/mod.rs b/crates/rspack_binding_options/src/options/raw_module/mod.rs
index 08bfdedf39da..b96b92eb1709 100644
--- a/crates/rspack_binding_options/src/options/raw_module/mod.rs
+++ b/crates/rspack_binding_options/src/options/raw_module/mod.rs
@@ -622,7 +622,7 @@ pub struct RawCssGeneratorOptions {
   #[napi(ts_type = r#""as-is" | "camel-case" | "camel-case-only" | "dashes" | "dashes-only""#)]
   pub exports_convention: Option<String>,
   pub exports_only: Option<bool>,
-  pub es_module: bool,
+  pub es_module: Option<bool>,
 }
 
 impl From<RawCssGeneratorOptions> for CssGeneratorOptions {
@@ -642,7 +642,7 @@ pub struct RawCssAutoGeneratorOptions {
   pub exports_convention: Option<String>,
   pub exports_only: Option<bool>,
   pub local_ident_name: Option<String>,
-  pub es_module: bool,
+  pub es_module: Option<bool>,
 }
 
 impl From<RawCssAutoGeneratorOptions> for CssAutoGeneratorOptions {
@@ -663,7 +663,7 @@ pub struct RawCssModuleGeneratorOptions {
   pub exports_convention: Option<String>,
   pub exports_only: Option<bool>,
   pub local_ident_name: Option<String>,
-  pub es_module: bool,
+  pub es_module: Option<bool>,
 }
 
 impl From<RawCssModuleGeneratorOptions> for CssModuleGeneratorOptions {
diff --git a/crates/rspack_core/src/options/module.rs b/crates/rspack_core/src/options/module.rs
index f7709a31f048..042690a5ad8c 100644
--- a/crates/rspack_core/src/options/module.rs
+++ b/crates/rspack_core/src/options/module.rs
@@ -337,7 +337,7 @@ impl From<String> for DataUrlEncoding {
 pub struct CssGeneratorOptions {
   pub exports_convention: Option<CssExportsConvention>,
   pub exports_only: Option<bool>,
-  pub es_module: bool,
+  pub es_module: Option<bool>,
 }
 
 #[derive(Debug, Clone, MergeFrom)]
@@ -345,7 +345,7 @@ pub struct CssAutoGeneratorOptions {
   pub exports_convention: Option<CssExportsConvention>,
   pub exports_only: Option<bool>,
   pub local_ident_name: Option<LocalIdentName>,
-  pub es_module: bool,
+  pub es_module: Option<bool>,
 }
 
 #[derive(Debug, Clone, MergeFrom)]
@@ -353,7 +353,7 @@ pub struct CssModuleGeneratorOptions {
   pub exports_convention: Option<CssExportsConvention>,
   pub exports_only: Option<bool>,
   pub local_ident_name: Option<LocalIdentName>,
-  pub es_module: bool,
+  pub es_module: Option<bool>,
 }
 
 #[derive(Debug, Clone, MergeFrom)]
diff --git a/crates/rspack_plugin_css/src/plugin/impl_plugin_for_css_plugin.rs b/crates/rspack_plugin_css/src/plugin/impl_plugin_for_css_plugin.rs
index ccf39fb286d6..975c3a973f3d 100644
--- a/crates/rspack_plugin_css/src/plugin/impl_plugin_for_css_plugin.rs
+++ b/crates/rspack_plugin_css/src/plugin/impl_plugin_for_css_plugin.rs
@@ -343,7 +343,7 @@ impl Plugin for CssPlugin {
           local_ident_name: None,
           exports_only: g.exports_only.expect("should have exports_only"),
           named_exports: p.named_exports.expect("should have named_exports"),
-          es_module: g.es_module,
+          es_module: g.es_module.expect("should have es_module"),
         }) as Box<dyn ParserAndGenerator>
       }),
     );
@@ -368,7 +368,7 @@ impl Plugin for CssPlugin {
           ),
           exports_only: g.exports_only.expect("should have exports_only"),
           named_exports: p.named_exports.expect("should have named_exports"),
-          es_module: g.es_module,
+          es_module: g.es_module.expect("should have es_module"),
         }) as Box<dyn ParserAndGenerator>
       }),
     );
@@ -393,7 +393,7 @@ impl Plugin for CssPlugin {
           ),
           exports_only: g.exports_only.expect("should have exports_only"),
           named_exports: p.named_exports.expect("should have named_exports"),
-          es_module: g.es_module,
+          es_module: g.es_module.expect("should have es_module"),
         }) as Box<dyn ParserAndGenerator>
       }),
     );
diff --git a/packages/rspack/src/config/adapter.ts b/packages/rspack/src/config/adapter.ts
index 22738a02898a..6c2537364f1e 100644
--- a/packages/rspack/src/config/adapter.ts
+++ b/packages/rspack/src/config/adapter.ts
@@ -767,7 +767,7 @@ function getRawCssGeneratorOptions(
 	return {
 		exportsConvention: options.exportsConvention,
 		exportsOnly: options.exportsOnly,
-		esModule: options.esModule!
+		esModule: options.esModule
 	};
 }
 
@@ -778,7 +778,7 @@ function getRawCssAutoOrModuleGeneratorOptions(
 		localIdentName: options.localIdentName,
 		exportsConvention: options.exportsConvention,
 		exportsOnly: options.exportsOnly,
-		esModule: options.esModule!
+		esModule: options.esModule
 	};
 }