diff --git a/lua/ts.lua b/lua/ts.lua
index 51c95d1..5f2fab3 100644
--- a/lua/ts.lua
+++ b/lua/ts.lua
@@ -133,11 +133,12 @@ local function build(repo, parser)
 end
 
 ---@param pack_name string
----@return string
+---@return string? lang
+---@return string? err
 local function lang_from_name(pack_name)
     local lang = pack_name:match("^tree%-sitter%-(.+)$")
     if not lang then
-        error("cannot derive lang from pack name: " .. pack_name)
+        return nil, "cannot derive lang from pack name: " .. pack_name
     end
     return lang
 end
@@ -161,7 +162,7 @@ local function pick(child, parent)
 end
 
 ---@param entry string | ow.TS.RepoOpts
----@return ow.TS.Repo
+---@return ow.TS.Repo?
 local function normalize(entry)
     ---@type ow.TS.RepoOpts
     local opts
@@ -187,8 +188,17 @@ local function normalize(entry)
         end
     else
         ---@cast opts ow.TS.SingleRepoOpts
+        local lang = opts.lang
+        if not lang then
+            local derived, err = lang_from_name(name)
+            if not derived then
+                log.error("Skipping %s: %s", name, err)
+                return nil
+            end
+            lang = derived
+        end
         table.insert(parsers, {
-            lang = opts.lang or lang_from_name(name),
+            lang = lang,
             location = opts.location,
             generate = opts.generate,
             from_json = opts.from_json,
@@ -206,7 +216,13 @@ end
 ---@param opts (string | ow.TS.RepoOpts)[]
 function M.setup(opts)
     ---@type ow.TS.Repo[]
-    local repos = vim.tbl_map(normalize, opts)
+    local repos = {}
+    for _, entry in ipairs(opts) do
+        local repo = normalize(entry)
+        if repo then
+            table.insert(repos, repo)
+        end
+    end
 
     ---@type vim.pack.Spec[]
     local pack_specs = vim.tbl_map(function(p)