diff --git a/frb_codegen/src/library/codegen/generator/api_dart/spec_generator/mod.rs b/frb_codegen/src/library/codegen/generator/api_dart/spec_generator/mod.rs
index 4e34035cc6..08fc97fd9b 100644
--- a/frb_codegen/src/library/codegen/generator/api_dart/spec_generator/mod.rs
+++ b/frb_codegen/src/library/codegen/generator/api_dart/spec_generator/mod.rs
@@ -40,6 +40,7 @@ pub(crate) struct ApiDartOutputSpecItem {
     pub funcs: Vec<ApiDartGeneratedFunction>,
     pub classes: Vec<ApiDartGeneratedClass>,
     pub imports: DartBasicHeaderCode,
+    pub preamble: String,
     pub unused_types: Vec<String>,
     pub needs_freezed: bool,
 }
@@ -134,6 +135,7 @@ fn generate_item(
         funcs,
         classes,
         imports,
+        preamble: context.config.dart_preamble.clone(),
         unused_types,
         needs_freezed,
     })
diff --git a/frb_codegen/src/library/codegen/generator/api_dart/text_generator.rs b/frb_codegen/src/library/codegen/generator/api_dart/text_generator.rs
index dca717eaaf..9aef083dd6 100644
--- a/frb_codegen/src/library/codegen/generator/api_dart/text_generator.rs
+++ b/frb_codegen/src/library/codegen/generator/api_dart/text_generator.rs
@@ -59,8 +59,10 @@ fn generate_end_api_text(
     // TODO use relative path calculation
     let path_frb_generated = "../".repeat(path_chunks_len - 2) + "frb_generated.dart";
 
+    let preamble = &item.preamble.as_str();
     let mut header = DartBasicHeaderCode {
         file_top: generate_code_header()
+            + if !preamble.is_empty() {"\n\n"} else {""} + preamble
             + "\n\n// ignore_for_file: invalid_use_of_internal_member, unused_import, unnecessary_import\n",
         import: format!(
             "