diff --git a/src/drivers/telemetry/iridiumsbd/IridiumSBD.cpp b/src/drivers/telemetry/iridiumsbd/IridiumSBD.cpp
index 19a7ec7fdc..2c44f84cc7 100644
--- a/src/drivers/telemetry/iridiumsbd/IridiumSBD.cpp
+++ b/src/drivers/telemetry/iridiumsbd/IridiumSBD.cpp
@@ -165,7 +165,7 @@ int IridiumSBD::ioctl(struct file *filp, int cmd, unsigned long arg)
 			return OK;
 		}
 
-	case FIONWRITE: {
+	case FIONSPACE: {
 			int count = SATCOM_TX_BUF_LEN - tx_buf_write_idx;
 			*(int *)arg = count;