diff --git a/binutils/ChangeLog b/binutils/ChangeLog
index 23a8d8eafa..6915027284 100644
--- a/binutils/ChangeLog
+++ b/binutils/ChangeLog
@@ -1,3 +1,8 @@
+2021-02-07  Alan Modra  <amodra@gmail.com>
+
+	* unwind-ia64.c (unw_print_xyreg): Don't leave output buffer
+	uninitialised on invalid input.
+
 2021-02-06  Alan Modra  <amodra@gmail.com>
 
 	PR 27349
diff --git a/binutils/unwind-ia64.c b/binutils/unwind-ia64.c
index 6eef917a6a..fb22f3fd54 100644
--- a/binutils/unwind-ia64.c
+++ b/binutils/unwind-ia64.c
@@ -156,6 +156,10 @@ unw_print_xyreg (char *cp, unsigned int x, unsigned int ytreg)
     case 2: /* br */
       sprintf (cp, "b%u", (ytreg & 0x1f));
       break;
+
+    default:
+      strcpy (cp, "invalid");
+      break;
     }
 }