diff --git a/base.h b/base.h
index b8846d8..4432b21 100644
--- a/base.h
+++ b/base.h
@@ -100,6 +100,7 @@ static bool is_valid_glyph(Glyph c) {
     return true;
   switch (c) {
   case '!':
+  case '?':
   case '.':
   case '*':
   case ':':