diff --git a/syntax/beluga.vim b/syntax/beluga.vim
index 78b4391..da736ec 100644
--- a/syntax/beluga.vim
+++ b/syntax/beluga.vim
@@ -84,3 +84,6 @@ hi def link belIf Keyword
 syn match belugaError /<-\|←/
 syn keyword belugaError prop
 hi def link belugaError Error
+
+syn match belugaHole /\<?\k*\>/
+hi def link belugaHole Underlined