diff --git a/src/ChangeLog b/src/ChangeLog
index f84fe133c7e..24343faa407 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,8 @@
+2014-07-04  Eli Zaretskii  <eliz@gnu.org>
+
+	* w32.c (network_interface_info): Make sure the argument is a
+	Lisp string.
+
 2014-07-01  Eli Zaretskii  <eliz@gnu.org>
 
 	* dispnew.c (prepare_desired_row): Accept 2 additional arguments:
diff --git a/src/w32.c b/src/w32.c
index 0892f932bc2..15e53600d95 100644
--- a/src/w32.c
+++ b/src/w32.c
@@ -8611,6 +8611,7 @@ network_interface_list (void)
 Lisp_Object
 network_interface_info (Lisp_Object ifname)
 {
+  CHECK_STRING (ifname);
   return network_interface_get_info (ifname);
 }