diff --git a/libserialport.h.in b/libserialport.h.in
index 88628fc..d945d4f 100644
--- a/libserialport.h.in
+++ b/libserialport.h.in
@@ -109,7 +109,7 @@ enum sp_mode {
 	SP_MODE_READ = 1,
 	/** Open port for write access. */
 	SP_MODE_WRITE = 2,
-	/** Open port for read and write access. */
+	/** Open port for read and write access. @since 0.1.1 */
 	SP_MODE_READ_WRITE = 3
 };
 
@@ -231,13 +231,17 @@ enum sp_signal {
 	SP_SIG_RI = 8
 };
 
-/** Transport types. */
+/**
+ * Transport types.
+ *
+ * @since 0.1.1
+ */
 enum sp_transport {
-	/** Native platform serial port. */
+	/** Native platform serial port. @since 0.1.1 */
 	SP_TRANSPORT_NATIVE,
-	/** USB serial port adapter. */
+	/** USB serial port adapter. @since 0.1.1 */
 	SP_TRANSPORT_USB,
-	/** Bluetooth serial port adapter. */
+	/** Bluetooth serial port adapter. @since 0.1.1 */
 	SP_TRANSPORT_BLUETOOTH
 };