diff --git a/core/src/ops/element_wise.rs b/core/src/ops/element_wise.rs
index bbd2a4ea12..3d7cf43257 100644
--- a/core/src/ops/element_wise.rs
+++ b/core/src/ops/element_wise.rs
@@ -197,7 +197,7 @@ macro_rules! element_wise {
                 $(
                     $(
                        $(
-                        let input_dt = t.datum_type();
+                        let mut input_dt = t.datum_type();
                         let sout_dt = out_dt.unwrap_or(input_dt);
                         if sout_dt.unquantized() == <$typ_dt>::datum_type().unquantized() {
                            if input_dt.unquantized() != sout_dt.unquantized() {
@@ -207,6 +207,7 @@ macro_rules! element_wise {
                                    DatumType::I8 => t.clone().into_arc_tensor().offset_i8_as_u8(),
                                    unknown_dt => bail!("unexpected quantization input dt {:?}", unknown_dt)
                                }.into_tensor();
+                               input_dt = t.datum_type(); // because zero_point change
                            }
                            unsafe { t.set_datum_type(sout_dt) } // force cast
                            let t: &mut[$typ_dt] = t.as_slice_mut::<$typ_dt>()?;
diff --git a/data/src/tensor.rs b/data/src/tensor.rs
index 8e8609e544..7f3fb68504 100644
--- a/data/src/tensor.rs
+++ b/data/src/tensor.rs
@@ -1470,7 +1470,7 @@ impl Tensor {
         t.into_arc_tensor()
     }
 
-    /// Offsets the tensor as an u8 type if it's an u8 type, otherwise passes it unchanged.
+    /// Offsets the tensor as an u8 type if it's an i8 type, otherwise passes it unchanged.
     pub fn offset_i8_as_u8(self: &Arc<Self>) -> Arc<Self> {
         let mut t = if let DatumType::I8 = self.dt.unquantized() {
             self.to_array_view::<i8>().unwrap().mapv(|v| (v as u8).wrapping_add(128)).into_tensor()