1 files changed, 2 insertions, 0 deletions
diff --git a/transcode.c b/transcode.c
index 22b44d8280..01f3245742 100644
--- a/transcode.c
+++ b/transcode.c
@@ -674,6 +674,8 @@ transcode_restartable0(const unsigned char **in_pos, unsigned char **out_pos,
             goto invalid;
 	  case UNDEF:
 	    goto undef;
+	  default:
+	  	rb_raise(rb_eRuntimeError, "unknown transcoding instruction");
 	}
 	continue;