[Bug #998066] Mention result mismatch
diff --git a/Doc/lib/libpopen2.tex b/Doc/lib/libpopen2.tex
index e35d37f..35faff6 100644
--- a/Doc/lib/libpopen2.tex
+++ b/Doc/lib/libpopen2.tex
@@ -30,6 +30,8 @@
\UNIX. This information is not available when using the
\function{popen2()}, \function{popen3()}, and \function{popen4()}
functions, or the equivalent functions in the \refmodule{os} module.
+(Note that the tuples returned by the \module{os} module's functions
+are in a different order from the ones returned by the \module{popen2} module.)
\begin{funcdesc}{popen2}{cmd\optional{, bufsize\optional{, mode}}}
Executes \var{cmd} as a sub-process. Returns the file objects