diff --git a/src/lib.rs b/src/lib.rs
index 264715b..b3e564e 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -18,15 +18,15 @@ impl ModelType {
         model_path: &str,
         device: Option<&Device>,
         dtype: Option<DType>,
-    ) -> Result<Box<impl GenerateModel>> {
+    ) -> Result<Box<dyn GenerateModel>> {
         match model_type {
             ModelType::Qwen2_5VL => {
                 let model = Qwen2_5VLGenerateModel::init(model_path, device, dtype)?;
-                Ok(Box::new(model))
+                Ok(Box::new(model) as Box<dyn GenerateModel>)
             },
             ModelType::MiniCPM4 => {
                 let model = MiniCPMGenerateModel::init(model_path, device, dtype)?;
-                Ok(Box::new(model))  
+                Ok(Box::new(model)as Box<dyn GenerateModel>)
             }
         }
     }
diff --git a/src/models/mod.rs b/src/models/mod.rs
index c84b1dd..120e531 100644
--- a/src/models/mod.rs
+++ b/src/models/mod.rs
@@ -1,6 +1,6 @@
-pub mod qwen2_5vl;
-pub mod minicpm4;
 pub mod base_modules;
+pub mod minicpm4;
+pub mod qwen2_5vl;
 
 use anyhow::Result;
 use candle_core::{DType, Device};
@@ -17,5 +17,7 @@ pub trait GenerateModel {
     fn generate_stream(
         &mut self,
         mes: ChatCompletionParameters,
-    ) -> Result<impl Stream<Item = Result<ChatCompletionChunkResponse, anyhow::Error>>>;
+    ) -> Result<impl Stream<Item = Result<ChatCompletionChunkResponse, anyhow::Error>>>
+    where
+        Self: Sized;
 }