diff --git a/src/modem.rs b/src/modem.rs
index a8e82a8..82b55f3 100644
--- a/src/modem.rs
+++ b/src/modem.rs
@@ -33,12 +33,12 @@ impl std::fmt::Display for ModemError {
 
 pub struct IterableRx<UART: serial::Uart> {
     inner: Rx<UART>,
-    timeout: Option<Duration>,
+    timeout: Duration,
 }
 
 impl<UART: serial::Uart> IterableRx<UART> {
     fn reset(&mut self, timeout: Duration) -> &mut Self {
-        self.timeout = Some(timeout);
+        self.timeout = timeout;
         self
     }
 }
@@ -50,19 +50,19 @@ impl<UART: serial::Uart> Iterator for IterableRx<UART> {
     /// interest, so the retry mechanism is triggered on _any_ error every 200ms until a byte is
     /// received, or the timeout is reached.
     fn next(&mut self) -> Option<Self::Item> {
-        let now = Instant::now();
+        let start = Instant::now();
         loop {
-            let timeout = self.timeout.unwrap_or(Duration::from_millis(0));
             match self.inner.read() {
                 Ok(b) => {
+                    self.timeout = self.timeout.saturating_sub(start.elapsed());
                     break Some(b)
                 },
-                _ => {
-                    if now.elapsed() > timeout {
+                Err(_) => {
+                    if start.elapsed() > self.timeout {
+                        self.timeout = Duration::from_millis(0);
                         break None
                     }
                     thread::sleep(Duration::from_millis(200));
-                    self.timeout = Some(timeout.saturating_sub(now.elapsed()));
                 }
             }
         }
@@ -72,7 +72,7 @@ impl<UART: serial::Uart> Iterator for IterableRx<UART> {
 impl<UART: serial::Uart> Modem<UART> {
     pub fn new(tx: Tx<UART>, rx: Rx<UART>) -> Self {
         Self {
-            rx: IterableRx { inner: rx, timeout: None },
+            rx: IterableRx { inner: rx, timeout: Duration::from_millis(0) },
             tx,
         }
     }