missingfield.diff

diff --git a/src/message.rs b/src/message.rs
index aa98505..252a06d 100644
--- a/src/message.rs
+++ b/src/message.rs
@@ -125,7 +125,9 @@ impl<'de> Visitor<'de> for MessageVisitor {
                 let params: Params = match name {
                     Command::WebDriver(ref cmd) => match cmd {
                         FindElement => {
-                            Params::Locator(seq.next_element::<webdriver::Locator>()?.unwrap())
+                            let locator = seq.next_element::<webdriver::Locator>()?
+                                .ok_or_else(|| de::Error::missing_field("missing parameters!"))?;
+                            Params::Locator(locator)
                         }
                         GetTimeouts => Params::None,
                     },