diff --git a/tcx/src/error_handling.rs b/tcx/src/error_handling.rs
index 26755d97..4a768afb 100644
--- a/tcx/src/error_handling.rs
+++ b/tcx/src/error_handling.rs
@@ -11,15 +11,17 @@ thread_local! {
 
 #[cfg_attr(tarpaulin, skip)]
 #[allow(irrefutable_let_patterns)]
-fn notify_err(err: Error) {
+fn notify_err(err: Error) -> Error {
     if let _backtrace = err.backtrace() {
         LAST_BACKTRACE.with(|e| {
             *e.borrow_mut() = Some((None, Backtrace::new()));
         });
     }
+    let display_err = format_err!("{}", &err);
     LAST_ERROR.with(|e| {
         *e.borrow_mut() = Some(err);
     });
+    display_err
 }
 
 fn lock_all_keystore() {
@@ -32,11 +34,11 @@ fn lock_all_keystore() {
 /// catch any error and format to string
 /// ref: <https://doc.rust-lang.org/edition-guide/rust-2018/error-handling-and-panics/controlling-panics-with-std-panic.html>
 #[cfg_attr(tarpaulin, skip)]
-pub unsafe fn landingpad<F: FnOnce() -> Result<T> + panic::UnwindSafe, T>(f: F) -> T {
+pub unsafe fn landingpad<F: FnOnce() -> Result<T> + panic::UnwindSafe, T>(f: F) -> Result<T> {
     match panic::catch_unwind(f) {
         Ok(rv) => {
             lock_all_keystore();
-            rv.map_err(notify_err).unwrap_or_else(|_| mem::zeroed())
+            rv.map_err(notify_err)
         }
         Err(err) => {
             lock_all_keystore();
@@ -49,8 +51,7 @@ pub unsafe fn landingpad<F: FnOnce() -> Result<T> + panic::UnwindSafe, T>(f: F)
                     None => "Box<Any>",
                 },
             };
-            notify_err(format_err!("{}", msg));
-            mem::zeroed()
+            Err(notify_err(format_err!("{}", msg)))
         }
     }
 }
diff --git a/tcx/src/lib.rs b/tcx/src/lib.rs
index ad809ffe..50178e9e 100644
--- a/tcx/src/lib.rs
+++ b/tcx/src/lib.rs
@@ -10,6 +10,8 @@ use crate::api::{Response, TcxAction};
 
 pub mod error_handling;
 pub mod handler;
+use failure::Error;
+use std::result;
 
 use crate::error_handling::{landingpad, LAST_BACKTRACE, LAST_ERROR};
 #[allow(deprecated)]
@@ -39,6 +41,8 @@ lazy_static! {
     pub static ref IS_DEBUG: RwLock<bool> = RwLock::new(false);
 }
 
+pub type Result<T> = result::Result<T, Error>;
+
 #[no_mangle]
 pub unsafe extern "C" fn free_const_string(s: *const c_char) {
     if s.is_null() {
@@ -57,7 +61,7 @@ pub unsafe extern "C" fn call_tcx_api(hex_str: *const c_char) -> *const c_char {
 
     let data = hex::decode(hex_str).expect("parse_arguments hex decode");
     let action: TcxAction = TcxAction::decode(data.as_slice()).expect("decode tcx api");
-    let reply: Vec<u8> = match action.method.to_lowercase().as_str() {
+    let reply: Result<Vec<u8>> = match action.method.to_lowercase().as_str() {
         "init_token_core_x" => landingpad(|| {
             handler::init_token_core_x(&action.param.unwrap().value).unwrap();
             Ok(vec![])
@@ -117,9 +121,13 @@ pub unsafe extern "C" fn call_tcx_api(hex_str: *const c_char) -> *const c_char {
         "unlock_then_crash" => landingpad(|| unlock_then_crash(&action.param.unwrap().value)),
         _ => landingpad(|| Err(format_err!("unsupported_method"))),
     };
-
-    let ret_str = hex::encode(reply);
-    CString::new(ret_str).unwrap().into_raw()
+    match reply {
+        Ok(reply) => {
+            let ret_str = hex::encode(reply);
+            CString::new(ret_str).unwrap().into_raw()
+        }
+        _ => CString::new("").unwrap().into_raw(),
+    }
 }
 
 #[no_mangle]
@@ -136,13 +144,7 @@ pub unsafe extern "C" fn clear_err() {
 pub unsafe extern "C" fn get_last_err_message() -> *const c_char {
     LAST_ERROR.with(|e| {
         if let Some(ref err) = *e.borrow() {
-            let rsp = Response {
-                is_success: false,
-                error: err.to_string(),
-            };
-            let rsp_bytes = encode_message(rsp).expect("encode error");
-            let ret_str = hex::encode(rsp_bytes);
-            CString::new(ret_str).unwrap().into_raw()
+            CString::new(err.to_string()).unwrap().into_raw()
         } else {
             CString::new("").unwrap().into_raw()
         }