diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index f5448c31d80..1f8b8e57225 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,7 @@
+2018-10-03  Tom Tromey  <tom@tromey.com>
+
+	* namespace.c (add_using_directive): Don't pass NULL to memcpy.
+
 2018-10-03  Philippe Waroquiers  <philippe.waroquiers@skynet.be>
 
 	* tid-parse.c (tid_is_in_list): Fix wrong 'See' comment.
diff --git a/gdb/namespace.c b/gdb/namespace.c
index be998d9d491..85c0c4b14d7 100644
--- a/gdb/namespace.c
+++ b/gdb/namespace.c
@@ -111,8 +111,9 @@ add_using_directive (struct using_direct **using_directives,
   else
     newobj->declaration = declaration;
 
-  memcpy (newobj->excludes, excludes.data (),
-	  excludes.size () * sizeof (*newobj->excludes));
+  if (!excludes.empty ())
+    memcpy (newobj->excludes, excludes.data (),
+	    excludes.size () * sizeof (*newobj->excludes));
   newobj->excludes[excludes.size ()] = NULL;
 
   newobj->next = *using_directives;