diff --git a/make-pages/BuildVar.hs b/make-pages/BuildVar.hs
index 042d78e..d0e2052 100644
--- a/make-pages/BuildVar.hs
+++ b/make-pages/BuildVar.hs
@@ -98,11 +98,13 @@ chunks = reverse . go "" [] . trimEnd where
   go acc cs (c :. rest) = go (acc <> singleton c) cs rest
 
   splitVar s
-    | (var, s') <- Text.span isAlphaNum s,
+    | (var, s') <- Text.span isIdChar s,
       isLower (Text.head var)
     = (var, s')
   splitVar _ = error "invalid variable name"
 
+  isIdChar c = isAlphaNum c || c `elem` ['_', '\'']
+
   lit s = (Lit, toStrictText s)
 
   trimEnd = Text.dropWhileEnd isSpace