diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 99edafca61..1f32c02abd 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,8 @@
+2016-11-12  Tom Tromey  <tom@tromey.com>
+
+	* rust-lang.c (rust_get_disr_info): Use std::string in one more
+	spot.
+
 2016-11-11  Yao Qi  <yao.qi@linaro.org>
 
 	* spu-tdep.c (spu_software_single_step): Don't call
diff --git a/gdb/rust-lang.c b/gdb/rust-lang.c
index 295dae11ac..7d4bfc3342 100644
--- a/gdb/rust-lang.c
+++ b/gdb/rust-lang.c
@@ -222,7 +222,7 @@ rust_get_disr_info (struct type *type, const gdb_byte *valaddr,
          with the first field being the actual type works.  */
       const char *field_name = TYPE_NAME (TYPE_FIELD_TYPE (type, 0));
       const char *last = rust_last_path_segment (field_name);
-      ret.name = concat (TYPE_NAME (type), "::", last, (char *) NULL);
+      ret.name = std::string (TYPE_NAME (type)) + "::" + last;
       ret.field_no = RUST_ENCODED_ENUM_REAL;
       ret.is_encoded = 1;
       return ret;