diff --git a/src/bytecode.c b/src/bytecode.c
index 646ada96aa1..ae290c27352 100644
--- a/src/bytecode.c
+++ b/src/bytecode.c
@@ -130,7 +130,8 @@ Lisp_Object Qbytecode;
 #define Bmult 0137
 
 #define Bpoint 0140
-#define Bmark 0141 /* no longer generated as of v18 */
+/* Was Bmark in v17.  */
+#define Bsave_current_buffer 0141
 #define Bgoto_char 0142
 #define Binsert 0143
 #define Bpoint_max 0144
@@ -537,6 +538,10 @@ If the third argument is incorrect, Emacs may crash.")
 	  record_unwind_protect (save_excursion_restore, save_excursion_save ());
 	  break;
 
+	case Bsave_current_buffer:
+	  record_unwind_protect (Fset_buffer, Fcurrent_buffer ());
+	  break;
+
 	case Bsave_window_excursion:
 	  TOP = Fsave_window_excursion (TOP);
 	  break;