diff --git a/src/pcd.rs b/src/pcd.rs
index 1fd7d26..8d915d8 100644
--- a/src/pcd.rs
+++ b/src/pcd.rs
@@ -290,24 +290,21 @@ pub trait Pcd<'a>: Serialize + Deserialize<'a> {
         }
     }
 
-    fn is_hex_string(&self) -> bool { 
-        let value = match serde_json::to_value(self) {
-            Ok(v) => v,
-            Err(_) => return false
-        };
+    fn is_hex_string(&self, length: Option<usize>) -> Result<()> { 
+        let value = serde_json::to_value(self)?;
 
         match value {
             Value::String(s) => {
-                let vec = Vec::from_hex(&s);
-                if vec.is_err() {
-                    return false;
-                } else if vec.unwrap().len() != 32 {
-                    return false;
-                } else {
-                    return true;
+                let vec = Vec::from_hex(&s)?;
+                if let Some(len) = length {
+                    let got_length = vec.len();
+                    if got_length != len {
+                        return Err(Error::msg(format!("Wrong length: expected {}, got {}", len, got_length)));
+                    }
                 }
+                Ok(())
             }
-            _ => false
+            _ => Err(Error::msg("Not a string Value"))
         }
     }
 }