diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 53885e13fc7..8e38ada5ea0 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,9 @@
+2019-12-18  Tom Tromey  <tromey@adacore.com>
+
+	PR build/25268:
+	* gdbsupport/thread-pool.c (set_thread_name): Expect "int" return
+	type on macOS.  Add comment.
+
 2019-12-18  Simon Marchi  <simon.marchi@efficios.com>
 
 	* c-lang.c (c_get_string, asm_language_defn): Remove space
diff --git a/gdb/gdbsupport/thread-pool.c b/gdb/gdbsupport/thread-pool.c
index cd548956951..a8c5fb774d9 100644
--- a/gdb/gdbsupport/thread-pool.c
+++ b/gdb/gdbsupport/thread-pool.c
@@ -49,8 +49,10 @@ set_thread_name (int (*set_name) (pthread_t, const char *), const char *name)
   set_name (pthread_self (), name);
 }
 
+/* The macOS man page says that pthread_setname_np returns "void", but
+   the headers actually declare it returning "int".  */
 ATTRIBUTE_UNUSED static void
-set_thread_name (void (*set_name) (const char *), const char *name)
+set_thread_name (int (*set_name) (const char *), const char *name)
 {
   set_name (name);
 }