diff --git a/src/codec.rs b/src/codec.rs
index 3acf16b..1c31a8c 100644
--- a/src/codec.rs
+++ b/src/codec.rs
@@ -294,10 +294,7 @@ mod tests {
             let result = decode(b"CMD,FOO\r")
                 .deserialize::<SimpleCommand>()
                 .unwrap_err();
-            assert_matches!(
-                result,
-                ResponseError::InvalidFields(OkResponseError::UnexpectedValue)
-            );
+            assert_matches!(result, ResponseError::InvalidFields(OkResponseError));
         }
 
         fn decode(raw: &[u8]) -> RawResponse {
diff --git a/src/command/ok_response.rs b/src/command/ok_response.rs
index df2b236..f6595a6 100644
--- a/src/command/ok_response.rs
+++ b/src/command/ok_response.rs
@@ -3,12 +3,8 @@ use tokio_util::bytes::Bytes;
 use crate::command::Response;
 
 #[derive(Debug, thiserror::Error)]
-pub enum OkResponseError {
-    #[error("expected `OK`")]
-    UnexpectedValue,
-    #[error("expected one response field")]
-    WrongNumberOfFields,
-}
+#[error("expected `OK`")]
+pub struct OkResponseError;
 
 #[derive(Clone, Copy, Debug)]
 pub struct OkResponse;
@@ -18,7 +14,7 @@ impl Response for OkResponse {
 
     fn deserialize(raw_values: &[Bytes]) -> Result<Self, Self::Error> {
         if raw_values[0] != b"OK".as_ref() {
-            return Err(OkResponseError::UnexpectedValue);
+            return Err(OkResponseError);
         }
 
         Ok(Self)