diff --git a/lib/eth/query.ex b/lib/eth/query.ex
index 7984b66..9c93deb 100644
--- a/lib/eth/query.ex
+++ b/lib/eth/query.ex
@@ -155,17 +155,21 @@ defmodule ETH.Query do
       {:ok, hex_gas_estimate} ->
         {:ok, hex_gas_estimate |> convert_to_number |> convert(denomination) |> round}
 
-      error ->
-        error
+      {:error, error} ->
+        {:error, error}
     end
   end
 
   def estimate_gas!(transaction \\ %{data: ""}, denomaination \\ :wei)
 
   def estimate_gas!(transaction = %{to: _to, data: _data}, denomination) do
-    {:ok, hex_gas_estimate} = HttpClient.eth_estimate_gas(transaction)
+    case HttpClient.eth_estimate_gas(transaction) do
+      {:ok, hex_gas_estimate} ->
+        hex_gas_estimate |> convert_to_number |> convert(denomination) |> round
 
-    hex_gas_estimate |> convert_to_number |> convert(denomination) |> round
+      {:error, error} ->
+        {:error, error}
+    end
   end
 
   def convert_transaction_log(log) do
diff --git a/lib/eth/transaction.ex b/lib/eth/transaction.ex
index dd44035..f45fbc7 100644
--- a/lib/eth/transaction.ex
+++ b/lib/eth/transaction.ex
@@ -26,9 +26,12 @@ defmodule ETH.Transaction do
   def send_transaction(params, private_key) do
     set_default_from(params, private_key)
     |> build
-    |> sign_transaction(private_key)
-    |> Base.encode16()
-    |> send
+    |> case do
+      %{gas_limit: {:error, error}} -> {:error, error}
+      build -> sign_transaction(build, private_key)
+      |> Base.encode16()
+      |> send
+    end
   end
 
   def send_transaction(sender_wallet, receiver_wallet, value) when is_number(value) do