diff --git a/crates/oxc_isolated_declarations/src/inferrer.rs b/crates/oxc_isolated_declarations/src/inferrer.rs
index faa382708..21856c09b 100644
--- a/crates/oxc_isolated_declarations/src/inferrer.rs
+++ b/crates/oxc_isolated_declarations/src/inferrer.rs
@@ -3,12 +3,10 @@ use oxc_ast::ast::{
     ArrowFunctionExpression, BindingPatternKind, Expression, FormalParameter, Function, Statement,
     TSType, TSTypeAnnotation, UnaryExpression,
 };
-use oxc_span::{GetSpan, SPAN};
+use oxc_span::SPAN;
 
 use crate::{
-    diagnostics::{
-        array_inferred, inferred_type_of_class_expression, parameter_must_have_explicit_type,
-    },
+    diagnostics::{array_inferred, inferred_type_of_class_expression},
     return_type::FunctionReturnType,
     IsolatedDeclarations,
 };
@@ -101,12 +99,6 @@ impl<'a> IsolatedDeclarations<'a> {
                 // SAFETY: `ast.copy` is unsound! We need to fix.
                 Some(unsafe { self.ast.copy(&annotation.type_annotation) })
             } else {
-                if let Expression::TSAsExpression(expr) = &pattern.right {
-                    if !expr.type_annotation.is_keyword_or_literal() {
-                        self.error(parameter_must_have_explicit_type(expr.type_annotation.span()));
-                    }
-                }
-
                 self.infer_type_from_expression(&pattern.right)
             }
         } else {
diff --git a/crates/oxc_isolated_declarations/tests/fixtures/function-parameters.ts b/crates/oxc_isolated_declarations/tests/fixtures/function-parameters.ts
index 4e9efc68b..4d348e1cc 100644
--- a/crates/oxc_isolated_declarations/tests/fixtures/function-parameters.ts
+++ b/crates/oxc_isolated_declarations/tests/fixtures/function-parameters.ts
@@ -30,3 +30,5 @@ export const fooBad2 = ({a, b} = { a: 1, b: 2 }): number => {
 
 export function withAny(a: any = 1, b: string): void { }
 export function withUnknown(a: unknown = 1, b: string): void { }
+
+export function withTypeAssertion(a = /regular-repression-cannot-infer/ as any): void { }
\ No newline at end of file
diff --git a/crates/oxc_isolated_declarations/tests/snapshots/function-parameters.snap b/crates/oxc_isolated_declarations/tests/snapshots/function-parameters.snap
index 4a017d85c..e5769c27b 100644
--- a/crates/oxc_isolated_declarations/tests/snapshots/function-parameters.snap
+++ b/crates/oxc_isolated_declarations/tests/snapshots/function-parameters.snap
@@ -17,6 +17,7 @@ export declare function fooBad(): number;
 export declare const fooBad2: () => number;
 export declare function withAny(a: any, b: string): void;
 export declare function withUnknown(a: unknown, b: string): void;
+export declare function withTypeAssertion(a?: any): void;
 
 
 ==================== Errors ====================