diff --git a/src/modbus-rtu.c b/src/modbus-rtu.c
index fc8a8009..ebef9347 100644
--- a/src/modbus-rtu.c
+++ b/src/modbus-rtu.c
@@ -638,7 +638,7 @@ static int _modbus_rtu_connect(modbus_t *ctx)
        signals and so forth) will affect your process
 
        Timeouts are ignored in canonical input mode or when the
-       NDELAY option is set on the file via open or fcntl */
+       NONBLOCK option is set on the file via open or fcntl */
     flags = O_RDWR | O_NOCTTY | O_NONBLOCK | O_EXCL;
 #ifdef O_CLOEXEC
     flags |= O_CLOEXEC;
@@ -816,7 +816,7 @@ static int _modbus_rtu_connect(modbus_t *ctx)
        UNIX serial interface drivers provide the ability to
        specify character and packet timeouts. Two elements of the
        c_cc array are used for timeouts: VMIN and VTIME. Timeouts
-       are ignored in canonical input mode or when the NDELAY
+       are ignored in canonical input mode or when the NONBLOCK
        option is set on the file via open or fcntl.
 
        VMIN specifies the minimum number of characters to read. If
@@ -846,9 +846,9 @@ static int _modbus_rtu_connect(modbus_t *ctx)
        VTIME specifies the amount of time to wait for incoming
        characters in tenths of seconds. If VTIME is set to 0 (the
        default), reads will block (wait) indefinitely unless the
-       NDELAY option is set on the port with open or fcntl.
+       NONBLOCK option is set on the port with open or fcntl.
     */
-    /* Unused because we use open with the NDELAY option */
+    /* Unused because we use open with the NONBLOCK option */
     tios.c_cc[VMIN] = 0;
     tios.c_cc[VTIME] = 0;