1 files changed, 2 insertions, 0 deletions
diff --git a/src/process.c b/src/process.c
index 3c8d426b814..ffaa0598f9b 100644
--- a/src/process.c
+++ b/src/process.c
@@ -2331,6 +2331,8 @@ wait_reading_process_input (time_limit, microsecs, read_kbd, do_display)
 	      else if (nread == -1 && errno == EWOULDBLOCK)
 		;
 #endif
+	      /* ISC 4.1 defines both EWOULDBLOCK and O_NONBLOCK,
+		 and Emacs uses O_NONBLOCK, so what we get is EAGAIN.  */
 #ifdef O_NONBLOCK
 	      else if (nread == -1 && errno == EAGAIN)
 		;