diff --git a/src/cmd/ksh93/sh.1 b/src/cmd/ksh93/sh.1
index 3aadca961..b663c17e4 100644
--- a/src/cmd/ksh93/sh.1
+++ b/src/cmd/ksh93/sh.1
@@ -1704,6 +1704,9 @@ discipline function is invoked.
 .TP
 .B .sh.subshell
 The current depth for subshells and command substitution.
+This value only counts the level of virtual (non-forked)
+subshells and is reset to zero if and when something
+requires a subshell environment to fork its own process.
 .TP
 .B .sh.value
 Set to the value of the variable at the time that the