diff --git a/backend-golang/file.go b/backend-golang/file.go
index 02ebe34..104f830 100644
--- a/backend-golang/file.go
+++ b/backend-golang/file.go
@@ -106,7 +106,7 @@ func (a *App) CopyFile(src string, dst string) error {
 	}
 	defer destFile.Close()
 
-	_, err = io.Copy(sourceFile, destFile)
+	_, err = io.Copy(destFile, sourceFile)
 	if err != nil {
 		return err
 	}
diff --git a/frontend/src/components/RunButton.tsx b/frontend/src/components/RunButton.tsx
index 07d5474..8daaa8b 100644
--- a/frontend/src/components/RunButton.tsx
+++ b/frontend/src/components/RunButton.tsx
@@ -138,12 +138,16 @@ export const RunButton: FC<{ onClickRun?: MouseEventHandler, iconMode?: boolean
             let customCudaFile = '';
             if (modelConfig.modelParameters.useCustomCuda) {
               customCudaFile = getSupportedCustomCudaFile();
-              if (customCudaFile)
+              if (customCudaFile) {
+                FileExists('./py310/Lib/site-packages/rwkv/model.py').then((exist) => {
+                  // defensive measure. As Python has already been launched, will only take effect the next time it runs.
+                  if (!exist) CopyFile('./backend-python/wkv_cuda_utils/wkv_cuda_model.py', './py310/Lib/site-packages/rwkv/model.py');
+                });
                 await CopyFile(customCudaFile, './py310/Lib/site-packages/rwkv/wkv_cuda.pyd').catch(() => {
                   customCudaFile = '';
                   toast(t('Failed to copy custom cuda file'), { type: 'error' });
                 });
-              else
+              } else
                 toast(t('Supported custom cuda file not found'), { type: 'warning' });
             }