diff --git a/src/os/unix/ngx_socket.c b/src/os/unix/ngx_socket.c
index a93679f64..c2fbc3bed 100644
--- a/src/os/unix/ngx_socket.c
+++ b/src/os/unix/ngx_socket.c
@@ -9,9 +9,9 @@
 
 
 /*
- * ioctl(FIONBIO) sets a blocking mode with the single syscall
- * while fcntl(F_SETFL, !O_NONBLOCK) needs to learn before
- * the previous state using fcntl(F_GETFL).
+ * ioctl(FIONBIO) sets a non-blocking mode with the single syscall
+ * while fcntl(F_SETFL, O_NONBLOCK) needs to learn the current state
+ * using fcntl(F_GETFL).
  *
  * ioctl() and fcntl() are syscalls at least in FreeBSD 2.x, Linux 2.2
  * and Solaris 7.