diff --git a/src/lib.rs b/src/lib.rs
index 742a690..7f3b02f 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -135,6 +135,12 @@ mod records {
     }
 }
 
+#[derive(Debug)]
+enum ResponseError {
+    ColumnNumberMisMatch,
+    MissionColumn(String),
+}
+
 struct Response {
     data: HashMap<String, Vec<Field>>,
     counter: usize,
@@ -148,7 +154,7 @@ impl Response {
         }
     }
 
-    fn add(&mut self, rec: Record) -> Result<(), String> {
+    fn add(&mut self, rec: Record) -> Result<(), ResponseError> {
         if self.data.is_empty() {
             for (key, value) in rec.iter() {
                 let mut store = Vec::new();
@@ -157,12 +163,12 @@ impl Response {
             }
         } else {
             if rec.len() != self.data.len() {
-                return Err("incorrect number of columns".to_string());
+                return Err(ResponseError::ColumnNumberMisMatch);
             }
             for (key, value) in rec.iter() {
                 match self.data.get_mut(key) {
                     Some(data) => data.push(value.clone()),
-                    None => return Err("bad".to_string()),
+                    None => return Err(ResponseError::MissionColumn(key.to_string())),
                 }
             }
         }
@@ -244,7 +250,10 @@ mod responses {
         res.add(rec1).unwrap();
         match res.add(rec2) {
             Ok(_) => unreachable!("Should not accept additional value"),
-            Err(_) => {}
+            Err(err) => match err {
+                ResponseError::ColumnNumberMisMatch => {}
+                _ => unreachable!("should havee been a mismatch error"),
+            },
         }
     }
 
@@ -259,7 +268,27 @@ mod responses {
         res.add(rec2).unwrap();
         match res.add(rec1) {
             Ok(_) => unreachable!("Should not accept additional value"),
-            Err(_) => {}
+            Err(err) => match err {
+                ResponseError::ColumnNumberMisMatch => {}
+                _ => unreachable!("should havee been a mismatch error"),
+            },
+        }
+    }
+
+    #[test]
+    fn wrong_column_name() {
+        let mut res = Response::new();
+        let mut rec1 = Record::new();
+        let mut rec2 = Record::new();
+        rec1.add("one", "one");
+        rec2.add("two", "two");
+        res.add(rec1).unwrap();
+        match res.add(rec2) {
+            Ok(_) => unreachable!("Should not accept additional value"),
+            Err(err) => match err {
+                ResponseError::MissionColumn(txt) => assert_eq!(txt, "two"),
+                _ => unreachable!("should have been missing cloumn"),
+            },
         }
     }
 }