diff --git a/Sources/TestingMacros/TestDeclarationMacro.swift b/Sources/TestingMacros/TestDeclarationMacro.swift
index 2274a4788..c98373469 100644
--- a/Sources/TestingMacros/TestDeclarationMacro.swift
+++ b/Sources/TestingMacros/TestDeclarationMacro.swift
@@ -314,7 +314,6 @@ public struct TestDeclarationMacro: PeerMacro, Sendable {
           thunkParam
         }
         FunctionParameterSyntax(
-          modifiers: [DeclModifierSyntax(name: .keyword(.isolated))],
           firstName: .wildcardToken(),
           type: "isolated (any Actor)?" as TypeSyntax,
           defaultValue: InitializerClauseSyntax(value: "Testing.__defaultSynchronousIsolationContext" as ExprSyntax)