diff --git a/std/process.d b/std/process.d
index 68cc65cfa..43fb53ffc 100644
--- a/std/process.d
+++ b/std/process.d
@@ -2159,6 +2159,8 @@ struct Config
         /**
         A function that is called before `exec` in $(LREF spawnProcess).
         It returns `true` if succeeded and otherwise returns `false`.
+        Please note that the code in this function must only use
+        async-signal-safe functions.
         On Windows, this member is not available.
         */
         bool function() nothrow @nogc @safe preExecFunction;