diff --git a/types/result.go b/types/result.go
index 78cea710c..6ebad8ab2 100644
--- a/types/result.go
+++ b/types/result.go
@@ -39,9 +39,9 @@ func (r ResponseCommit) Error() string {
 func fmtError(code CodeType, log string) string {
 	codeAsStr, ok := code2string[code]
 	if ok {
-		return fmt.Sprintf("%s (%v): %s", codeAsStr, code, log)
+		return fmt.Sprintf("%s (%d): %s", codeAsStr, code, log)
 	} else {
-		return fmt.Sprintf("Unknown error (%v): %s", code, log)
+		return fmt.Sprintf("Unknown error (%d): %s", code, log)
 	}
 }
 
@@ -69,3 +69,13 @@ func (r *ResponseQuery) Result() *ResultQuery {
 		Log:    r.Log,
 	}
 }
+
+// IsErr returns true if Code is something other than OK.
+func (r *ResultQuery) IsErr() bool {
+	return r.Code != CodeType_OK
+}
+
+// Error implements error interface by formatting result as string.
+func (r *ResultQuery) Error() string {
+	return fmtError(r.Code, r.Log)
+}
diff --git a/types/result_test.go b/types/result_test.go
new file mode 100644
index 000000000..14f334c49
--- /dev/null
+++ b/types/result_test.go
@@ -0,0 +1,76 @@
+package types
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestResultQuery(t *testing.T) {
+	orig := &ResponseQuery{
+		Code:   CodeType_OK,
+		Index:  0,
+		Key:    []byte("hello"),
+		Value:  []byte("world"),
+		Height: 1,
+	}
+	res := orig.Result()
+	assert.False(t, res.IsErr())
+
+	orig = &ResponseQuery{
+		Code:   CodeType_BadNonce,
+		Index:  0,
+		Key:    []byte("hello"),
+		Value:  []byte("world"),
+		Height: 1,
+		Log:    "bad",
+	}
+	res = orig.Result()
+	assert.True(t, res.IsErr())
+	assert.Equal(t, "Error bad nonce (3): bad", res.Error())
+}
+
+func TestResponseDeliverTx(t *testing.T) {
+	res := ResponseDeliverTx{
+		Code: CodeType_OK,
+		Data: []byte("Victor Mancha"),
+	}
+	assert.False(t, res.IsErr())
+
+	res = ResponseDeliverTx{
+		Code: CodeType_InternalError,
+		Log:  "bad",
+	}
+	assert.True(t, res.IsErr())
+	assert.Equal(t, "Internal error (1): bad", res.Error())
+}
+
+func TestResponseCheckTx(t *testing.T) {
+	res := ResponseCheckTx{
+		Code: CodeType_OK,
+		Data: []byte("Talos"),
+	}
+	assert.False(t, res.IsErr())
+
+	res = ResponseCheckTx{
+		Code: CodeType_InternalError,
+		Log:  "bad",
+	}
+	assert.True(t, res.IsErr())
+	assert.Equal(t, "Internal error (1): bad", res.Error())
+}
+
+func TestResponseCommit(t *testing.T) {
+	res := ResponseCommit{
+		Code: CodeType_OK,
+		Data: []byte("Old Lace"),
+	}
+	assert.False(t, res.IsErr())
+
+	res = ResponseCommit{
+		Code: CodeType_Unauthorized,
+		Log:  "bad",
+	}
+	assert.True(t, res.IsErr())
+	assert.Equal(t, "Unauthorized (4): bad", res.Error())
+}