diff --git a/src/filetransfer/mod.rs b/src/filetransfer/mod.rs
index 1a4d94b..9b2e1b5 100644
--- a/src/filetransfer/mod.rs
+++ b/src/filetransfer/mod.rs
@@ -32,7 +32,7 @@ use crate::fs::FsEntry;
 pub mod sftp_transfer;
 
 // Types
-type ProgressCallback = fn(bytes_written: usize, size: usize);
+pub type ProgressCallback = dyn Fn(usize, usize);
 
 /// ## FileTransferProtocol
 ///
@@ -125,7 +125,7 @@ pub trait FileTransfer {
     /// ### mkdir
     /// 
     /// Make directory
-    fn mkdir(&self, dir: String) -> Result<(), FileTransferError>;
+    fn mkdir(&self, dir: &Path) -> Result<(), FileTransferError>;
 
     /// ### remove
     /// 
@@ -142,11 +142,11 @@ pub trait FileTransfer {
     /// Send file to remote
     /// File name is referred to the name of the file as it will be saved
     /// Data contains the file data
-    fn send_file(&self, file_name: &Path, file: &mut File, prog_cb: Option<ProgressCallback>) -> Result<(), FileTransferError>;
+    fn send_file(&self, file_name: &Path, file: &mut File, prog_cb: Option<Box<ProgressCallback>>) -> Result<(), FileTransferError>;
 
     /// ### recv_file
     /// 
     /// Receive file from remote with provided name
-    fn recv_file(&self, file_name: &Path, dest_file: &mut File, prog_cb: Option<ProgressCallback>) -> Result<(), FileTransferError>;
+    fn recv_file(&self, file_name: &Path, dest_file: &mut File, prog_cb: Option<Box<ProgressCallback>>) -> Result<(), FileTransferError>;
 
 }
diff --git a/src/filetransfer/sftp_transfer.rs b/src/filetransfer/sftp_transfer.rs
index e8455e1..9d3488d 100644
--- a/src/filetransfer/sftp_transfer.rs
+++ b/src/filetransfer/sftp_transfer.rs
@@ -313,7 +313,7 @@ impl FileTransfer for SftpFileTransfer {
     /// ### mkdir
     ///
     /// Make directory
-    fn mkdir(&self, dir: String) -> Result<(), FileTransferError> {
+    fn mkdir(&self, dir: &Path) -> Result<(), FileTransferError> {
         match self.sftp.as_ref() {
             Some(sftp) => {
                 // Make directory
@@ -399,7 +399,7 @@ impl FileTransfer for SftpFileTransfer {
         &self,
         file_name: &Path,
         file: &mut File,
-        prog_cb: Option<ProgressCallback>,
+        prog_cb: Option<Box<ProgressCallback>>,
     ) -> Result<(), FileTransferError> {
         match self.sftp.as_ref() {
             None => Err(FileTransferError::UninitializedSession),
@@ -429,7 +429,7 @@ impl FileTransfer for SftpFileTransfer {
                                             return Err(FileTransferError::IoErr(err));
                                         }
                                         // Call callback
-                                        if let Some(cb) = prog_cb {
+                                        if let Some(ref cb) = prog_cb {
                                             cb(total_bytes_written, file_size);
                                         }
                                     }
@@ -452,7 +452,7 @@ impl FileTransfer for SftpFileTransfer {
         &self,
         file_name: &Path,
         dest_file: &mut File,
-        prog_cb: Option<ProgressCallback>,
+        prog_cb: Option<Box<ProgressCallback>>,
     ) -> Result<(), FileTransferError> {
         match self.sftp.as_ref() {
             None => Err(FileTransferError::UninitializedSession),
@@ -487,7 +487,7 @@ impl FileTransfer for SftpFileTransfer {
                                             return Err(FileTransferError::IoErr(err));
                                         }
                                         // Call callback
-                                        if let Some(cb) = prog_cb {
+                                        if let Some(ref cb) = prog_cb {
                                             cb(total_bytes_written, file_size);
                                         }
                                     }
@@ -699,7 +699,7 @@ mod tests {
             .recv_file(
                 PathBuf::from("readme.txt").as_path(),
                 &mut dst_file_hnd,
-                Some(progress_callback)
+                Some(Box::new(progress_callback))
             )
             .is_ok());
         // Disconnect
@@ -733,7 +733,7 @@ mod tests {
             .recv_file(
                 PathBuf::from("omar.txt").as_path(),
                 &mut dst_file_hnd,
-                Some(progress_callback)
+                Some(Box::new(progress_callback))
             )
             .is_err());
         // Disconnect
@@ -770,7 +770,7 @@ mod tests {
             .recv_file(
                 PathBuf::from("readme.txt").as_path(),
                 &mut dst_file_hnd,
-                Some(progress_callback)
+                Some(Box::new(progress_callback))
             )
             .is_err());
         // Disconnect