diff --git a/fio.1 b/fio.1
index b0276c4..ab147f2 100644
--- a/fio.1
+++ b/fio.1
@@ -379,7 +379,9 @@
 .RE
 .TP
 .BI iodepth \fR=\fPint
-Number of I/O units to keep in flight against the file.  Default: 1.
+Number of I/O units to keep in flight against the file. Note that increasing
+iodepth beyond 1 will not affect synchronous ioengines (except for small
+degress when verify_async is in use).  Default: 1.
 .TP
 .BI iodepth_batch \fR=\fPint
 Number of I/Os to submit at once.  Default: \fBiodepth\fR.