diff --git a/include/serial/serial.h b/include/serial/serial.h
index 82dc299..e25ec5c 100644
--- a/include/serial/serial.h
+++ b/include/serial/serial.h
@@ -450,6 +450,8 @@ public:
    * reading or writing is complete, when a timeout occurs, or when an
    * exception occurs.
    *
+   * A timeout of 0 enables non-blocking mode.
+   *
    * \param timeout A serial::Timeout struct containing the inter byte
    * timeout, and the read and write timeout constants and multipliers.
    *
diff --git a/src/impl/unix.cc b/src/impl/unix.cc
index 0ff251e..8a8f00d 100755
--- a/src/impl/unix.cc
+++ b/src/impl/unix.cc
@@ -617,12 +617,18 @@ Serial::SerialImpl::write (const uint8_t *data, size_t length)
   total_timeout_ms += timeout_.write_timeout_multiplier * static_cast<long> (length);
   MillisecondTimer total_timeout(total_timeout_ms);
 
+  bool first = true;
   while (bytes_written < length) {
     int64_t timeout_remaining_ms = total_timeout.remaining();
-    if (timeout_remaining_ms <= 0) {
+    // Only consider the timeout if it's not the first iteration of the loop
+    // otherwise a timeout of 0 won't be allowed through
+    if (!first && (timeout_remaining_ms <= 0)) {
       // Timed out
       break;
     }
+    if( first ) {
+      first = false;
+    }
     timespec timeout(timespec_from_ms(timeout_remaining_ms));
 
     FD_ZERO (&writefds);