diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 1c714ddba3f..70d4c067424 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,7 @@
+2018-11-29  Tom Tromey  <tom@tromey.com>
+
+	* valarith.c (value_x_unop): Don't set argvec[3].
+
 2018-11-26  Simon Marchi  <simon.marchi@ericsson.com>
 
 	PR gdb/23917
diff --git a/gdb/valarith.c b/gdb/valarith.c
index 3a59ada2d56..66cd9042d47 100644
--- a/gdb/valarith.c
+++ b/gdb/valarith.c
@@ -554,13 +554,11 @@ value_x_unop (struct value *arg1, enum exp_opcode op, enum noside noside)
     case UNOP_POSTINCREMENT:
       strcpy (ptr, "++");
       argvec[2] = value_from_longest (builtin_type (gdbarch)->builtin_int, 0);
-      argvec[3] = 0;
       nargs ++;
       break;
     case UNOP_POSTDECREMENT:
       strcpy (ptr, "--");
       argvec[2] = value_from_longest (builtin_type (gdbarch)->builtin_int, 0);
-      argvec[3] = 0;
       nargs ++;
       break;
     case UNOP_LOGICAL_NOT: