1 files changed, 4 insertions, 0 deletions

diff --git a/lispref/os.texi b/lispref/os.texi
index 6c4a86e3bbe..d6a58910f40 100644
--- a/lispref/os.texi
+++ b/lispref/os.texi
@@ -738,6 +738,10 @@ process-environment
     "HOME=/user/lewis")
 @end group
 @end smallexample
+
+If @code{process-environment} contains ``duplicate'' elements that
+specify the same environment variable, the first of these elements
+specifies the variable, and the other ``duplicates'' are ignored.
 @end defvar
 
 @defvar path-separator