diff --git a/common/session-env.c b/common/session-env.c
index f07d9d101..e774c1d9b 100644
--- a/common/session-env.c
+++ b/common/session-env.c
@@ -84,9 +84,10 @@ static struct
                                       modules (eg "xim").  */
   { "INSIDE_EMACS" },            /* Set by Emacs before running a
                                     process.  */
-  { "PINENTRY_USER_DATA", "pinentry-user-data"}
+  { "PINENTRY_USER_DATA", "pinentry-user-data"},
                                  /* Used for communication with
                                     non-standard Pinentries.  */
+  { "PINENTRY_GEOM_HINT" }       /* Used to pass window information. */
 };