diff --git a/client/rpc-api/src/author/error.rs b/client/rpc-api/src/author/error.rs
index e6ee36cdce19a..69c036be95fe0 100644
--- a/client/rpc-api/src/author/error.rs
+++ b/client/rpc-api/src/author/error.rs
@@ -20,6 +20,7 @@
 
 use crate::errors;
 use jsonrpc_core as rpc;
+use sp_runtime::transaction_validity::InvalidTransaction;
 
 /// Author RPC Result type.
 pub type Result<T> = std::result::Result<T, Error>;
@@ -114,10 +115,18 @@ impl From<Error> for rpc::Error {
 				message: format!("Verification Error: {}", e).into(),
 				data: Some(format!("{:?}", e).into()),
 			},
-			Error::Pool(PoolError::InvalidTransaction(e)) => rpc::Error {
+			Error::Pool(PoolError::InvalidTransaction(InvalidTransaction::Custom(e))) => rpc::Error {
 				code: rpc::ErrorCode::ServerError(POOL_INVALID_TX),
 				message: "Invalid Transaction".into(),
-				data: serde_json::to_value(e).ok(),
+				data: Some(format!("Custom error: {}", e).into()),
+			},
+			Error::Pool(PoolError::InvalidTransaction(e)) => {
+				let msg: &str = e.into();
+				rpc::Error {
+					code: rpc::ErrorCode::ServerError(POOL_INVALID_TX),
+					message: "Invalid Transaction".into(),
+					data: Some(msg.into()),
+				}
 			},
 			Error::Pool(PoolError::UnknownTransaction(e)) => rpc::Error {
 				code: rpc::ErrorCode::ServerError(POOL_UNKNOWN_VALIDITY),
diff --git a/client/transaction-pool/src/api.rs b/client/transaction-pool/src/api.rs
index 79315c2724b5b..c7665022a5623 100644
--- a/client/transaction-pool/src/api.rs
+++ b/client/transaction-pool/src/api.rs
@@ -64,7 +64,7 @@ where
 	Client: ProvideRuntimeApi<Block> + BlockBackend<Block> + BlockIdTo<Block>,
 	Client: Send + Sync + 'static,
 	Client::Api: TaggedTransactionQueue<Block>,
-	sp_api::ApiErrorFor<Client, Block>: Send,
+	sp_api::ApiErrorFor<Client, Block>: Send + std::fmt::Display,
 {
 	type Block = Block;
 	type Error = error::Error;
@@ -105,7 +105,7 @@ where
 				#[allow(deprecated)] // old validate_transaction
 				runtime_api.validate_transaction_before_version_2(&at, uxt)
 			};
-			let res = res.map_err(|e| Error::RuntimeApi(format!("{:?}", e)));
+			let res = res.map_err(|e| Error::RuntimeApi(e.to_string()));
 			if let Err(e) = tx.send(res) {
 				log::warn!("Unable to send a validate transaction result: {:?}", e);
 			}
diff --git a/primitives/runtime/src/transaction_validity.rs b/primitives/runtime/src/transaction_validity.rs
index fc2465a068fe3..1aad9e75aec34 100644
--- a/primitives/runtime/src/transaction_validity.rs
+++ b/primitives/runtime/src/transaction_validity.rs
@@ -104,7 +104,7 @@ impl From<InvalidTransaction> for &'static str {
 			InvalidTransaction::BadMandatory =>
 				"A call was labelled as mandatory, but resulted in an Error.",
 			InvalidTransaction::MandatoryDispatch =>
-				"Tranaction dispatch is mandatory; transactions may not have mandatory dispatches.",
+				"Transaction dispatch is mandatory; transactions may not have mandatory dispatches.",
 			InvalidTransaction::Custom(_) => "InvalidTransaction custom error",
 		}
 	}