diff --git a/crates/oxc_ast/src/ast/js.rs b/crates/oxc_ast/src/ast/js.rs
index 05d3652f5..1e135f138 100644
--- a/crates/oxc_ast/src/ast/js.rs
+++ b/crates/oxc_ast/src/ast/js.rs
@@ -1683,7 +1683,6 @@ pub struct Function<'a> {
     #[cfg_attr(feature = "serde", serde(flatten))]
     pub span: Span,
     pub id: Option<BindingIdentifier>,
-    pub expression: bool,
     pub generator: bool,
     pub r#async: bool,
     /// Declaring `this` in a Function <https://www.typescriptlang.org/docs/handbook/2/functions.html#declaring-this-in-a-function>
diff --git a/crates/oxc_ast/src/ast_builder.rs b/crates/oxc_ast/src/ast_builder.rs
index a4fae7a2a..14efe92a7 100644
--- a/crates/oxc_ast/src/ast_builder.rs
+++ b/crates/oxc_ast/src/ast_builder.rs
@@ -773,7 +773,6 @@ impl<'a> AstBuilder<'a> {
         r#type: FunctionType,
         span: Span,
         id: Option<BindingIdentifier>,
-        expression: bool,
         generator: bool,
         r#async: bool,
         this_param: Option<TSThisParameter<'a>>,
@@ -787,7 +786,6 @@ impl<'a> AstBuilder<'a> {
             r#type,
             span,
             id,
-            expression,
             generator,
             r#async,
             this_param,
diff --git a/crates/oxc_parser/src/js/function.rs b/crates/oxc_parser/src/js/function.rs
index 02556a393..d15cd87e1 100644
--- a/crates/oxc_parser/src/js/function.rs
+++ b/crates/oxc_parser/src/js/function.rs
@@ -125,7 +125,6 @@ impl<'a> Parser<'a> {
             function_type,
             self.end_span(span),
             id,
-            false, // expression
             generator,
             r#async,
             this_param,
diff --git a/crates/oxc_transformer/src/es2015/arrow_functions.rs b/crates/oxc_transformer/src/es2015/arrow_functions.rs
index 06817b50b..8e4b27ff7 100644
--- a/crates/oxc_transformer/src/es2015/arrow_functions.rs
+++ b/crates/oxc_transformer/src/es2015/arrow_functions.rs
@@ -127,7 +127,6 @@ impl<'a> ArrowFunctions<'a> {
                 FunctionType::FunctionExpression,
                 SPAN,
                 None,
-                false,
                 arrow_expr.generator,
                 arrow_expr.r#async,
                 None,
diff --git a/crates/oxc_transformer/src/proposals/decorators.rs b/crates/oxc_transformer/src/proposals/decorators.rs
index 84de116fd..994fb7baf 100644
--- a/crates/oxc_transformer/src/proposals/decorators.rs
+++ b/crates/oxc_transformer/src/proposals/decorators.rs
@@ -612,7 +612,6 @@ impl<'a> Decorators<'a> {
                                 None,
                                 false,
                                 false,
-                                false,
                                 None,
                                 self.ast.formal_parameters(
                                     SPAN,
diff --git a/crates/oxc_transformer/src/typescript/mod.rs b/crates/oxc_transformer/src/typescript/mod.rs
index 2b26fcf02..96c1fe08e 100644
--- a/crates/oxc_transformer/src/typescript/mod.rs
+++ b/crates/oxc_transformer/src/typescript/mod.rs
@@ -723,7 +723,6 @@ impl<'a> TypeScript<'a> {
                 None,
                 false,
                 false,
-                false,
                 None,
                 params,
                 Some(body),