diff --git a/lua/zettelkasten/options.lua b/lua/zettelkasten/options.lua
index f47d9a8..bf80889 100644
--- a/lua/zettelkasten/options.lua
+++ b/lua/zettelkasten/options.lua
@@ -7,17 +7,30 @@ local ANCHOR_SEPARATOR = "_"
 -- TODO zettel_root = vim.g["zettel_root"] or vim.b["zettel_root"] or "~/documents/notes",
 -- TODO zettel_anchor_pattern = regex? -> needs custom creation function in `create_anchor`
 
+-- constricted option sets
+local ZETTEL_LINK_STYLE_OPTIONS = {markdown = true, wiki = true}
+
+local function must_contain(set, value, name)
+    if type(set) ~= "table" then return false end
+    if not set[value] then
+        local allvalues = ""
+        for n, _ in pairs(set) do allvalues = n .. ", " .. allvalues end
+        error((name or "value") .. " " .. value .. " must be one of " ..
+                  allvalues:sub(1, -3))
+    end
+end
+
 function Opt.zettel()
     local options = {}
     options.extension =
         vim.g["zettel_extension"] or vim.b["zettel_extension"] or
             ZETTEL_EXTENSION
+
     options.link_style = vim.g["zettel_link_style"] or
                              vim.b["zettel_link_style"] or ZETTEL_LINK_STYLE
+    must_contain(ZETTEL_LINK_STYLE_OPTIONS, options.link_style,
+                 "zettel_link_style")
 
-    if options.link_style ~= "wiki" and options.link_style ~= "markdown" then
-        error("zettel_link_style can only be set to markdown or wiki.")
-    end
     return options
 end