diff --git a/doc/stdenv/stdenv.chapter.md b/doc/stdenv/stdenv.chapter.md
index 29b57e9f6d31..43795dfc94f6 100644
--- a/doc/stdenv/stdenv.chapter.md
+++ b/doc/stdenv/stdenv.chapter.md
@@ -599,6 +599,8 @@ Additional file types can be supported by setting the `unpackCmd` variable (see
 
 The list of source files or directories to be unpacked or copied. One of these must be set. Note that if you use `srcs`, you should also set `sourceRoot` or `setSourceRoot`.
 
+These should ideally actually be sources and licensed under a FLOSS license.  If you have to use a binary upstream release or package non-free software, make sure you correctly mark your derivation as such in the [`sourceProvenance`](#var-meta-sourceProvenance) and [`license`](#sec-meta-license) fields of the [`meta`](#chap-meta) section.
+
 ##### `sourceRoot` {#var-stdenv-sourceRoot}
 
 After unpacking all of `src` and `srcs`, if neither of `sourceRoot` and `setSourceRoot` are set, `unpackPhase` of the generic builder checks that the unpacking produced a single directory and moves the current working directory into it.