diff --git a/lua/duckbones/palette.lua b/lua/duckbones/palette.lua
index d61c2d1..7e00194 100644
--- a/lua/duckbones/palette.lua
+++ b/lua/duckbones/palette.lua
@@ -4,7 +4,7 @@ local hsluv = lush.hsluv
 
 local M = {}
 
-M.dark = util.palette_extend {
+M.dark = util.palette_extend({
 	bg = hsluv "#0f111b",
 	fg = hsluv "#ecf0c1",
 	rose = hsluv "#e33400",
@@ -14,6 +14,6 @@ M.dark = util.palette_extend {
 	blossom = hsluv "#7a5ccc",
 	blossom1 = hsluv "#b3a1e6",
 	sky = hsluv "#00a3cc",
-}
+}, "dark")
 
 return M
diff --git a/lua/forestbones/palette.lua b/lua/forestbones/palette.lua
index a4f6b3b..09d4d47 100644
--- a/lua/forestbones/palette.lua
+++ b/lua/forestbones/palette.lua
@@ -15,7 +15,7 @@ M.light = util.palette_extend({
 	sky = hsluv(151.6, 87.3, 61.5),
 }, "light")
 
-M.dark = util.palette_extend {
+M.dark = util.palette_extend({
 	bg = hsluv(232.6, 27, 20.7),
 	fg = hsluv(67.1, 26.4, 88), -- base: 67.1, 26.4, 80.3
 	rose = hsluv(11.3, 67.5, 64.4),
@@ -24,6 +24,6 @@ M.dark = util.palette_extend {
 	water = hsluv(179.5, 51, 71.8),
 	blossom = hsluv(339.1, 46.7, 69.8),
 	sky = hsluv(136.1, 45.8, 72.6),
-}
+}, "dark")
 
 return M
diff --git a/lua/neobones/palette.lua b/lua/neobones/palette.lua
index 015694f..bb11732 100644
--- a/lua/neobones/palette.lua
+++ b/lua/neobones/palette.lua
@@ -11,11 +11,11 @@ M.light = util.palette_extend({
 }, "light")
 M.light.leaf = M.light.leaf.sa(24).li(8) -- need to make green more prominent
 
-M.dark = util.palette_extend {
+M.dark = util.palette_extend({
 	bg = hsluv "#0f191f", -- --bg-color
 	fg = hsluv "#c7d6d0", -- --fg-color
 	leaf = hsluv "#8fff6d", -- --accent-color
 	water = hsluv "#8190d4", -- default blue looks to close to bg
-}
+}, "dark")
 
 return M
diff --git a/lua/nordbones/palette.lua b/lua/nordbones/palette.lua
index f9d6403..2124fbb 100644
--- a/lua/nordbones/palette.lua
+++ b/lua/nordbones/palette.lua
@@ -23,7 +23,7 @@ local base = {
 	nord15 = hsluv "#b48ead",
 }
 
-M.dark = util.palette_extend {
+M.dark = util.palette_extend({
 	bg = base.nord0,
 	fg = base.nord6,
 	rose = base.nord11,
@@ -32,7 +32,7 @@ M.dark = util.palette_extend {
 	water = base.nord7,
 	blossom = base.nord15,
 	sky = base.nord8,
-}
+}, "dark")
 
 M.base = base
 
diff --git a/lua/rosebones/palette.lua b/lua/rosebones/palette.lua
index c230ced..6faa2fe 100644
--- a/lua/rosebones/palette.lua
+++ b/lua/rosebones/palette.lua
@@ -16,7 +16,7 @@ M.light = util.palette_extend({
 	text = hsluv(270.1, 22.9, 36.8), -- text, base: 270.1, 22.9, 36.8
 }, "light")
 
-M.dark = util.palette_extend {
+M.dark = util.palette_extend({
 	bg = hsluv(271.2, 20.2, 8.5), -- base
 	bg_warm = hsluv(268.9, 24.5, 13.9), -- base moon
 	fg = hsluv(14.8, 23, 86), -- rose, base: 14.8, 59.9, 80.3
@@ -27,6 +27,6 @@ M.dark = util.palette_extend {
 	blossom = hsluv(283.1, 67.3, 73), -- iris
 	sky = hsluv(206.7, 42.9, 80), -- foam
 	text = hsluv(269.4, 56, 89.2), -- text, base: 269.4, 63.6, 89.2
-}
+}, "dark")
 
 return M
diff --git a/lua/tokyobones/palette.lua b/lua/tokyobones/palette.lua
index ba988f8..36ba9cb 100644
--- a/lua/tokyobones/palette.lua
+++ b/lua/tokyobones/palette.lua
@@ -17,7 +17,7 @@ M.light = util.palette_extend({
 	sky1 = hsluv "#33635c",
 }, "light")
 
-M.dark = util.palette_extend {
+M.dark = util.palette_extend({
 	bg = hsluv "#1a1b26",
 	bg_warm = hsluv "#24283b", -- storm
 	fg = hsluv "#c0caf5",
@@ -29,6 +29,6 @@ M.dark = util.palette_extend {
 	sky = hsluv "#2ac3de",
 	orange = hsluv "#ff9e64",
 	sky1 = hsluv "#73daca",
-}
+}, "dark")
 
 return M
diff --git a/lua/zenbones/palette.lua b/lua/zenbones/palette.lua
index 568ae55..73231d8 100644
--- a/lua/zenbones/palette.lua
+++ b/lua/zenbones/palette.lua
@@ -3,6 +3,6 @@ local util = require "zenbones.util"
 local M = {}
 
 M.light = util.palette_extend({}, "light")
-M.dark = util.palette_extend {}
+M.dark = util.palette_extend({}, "dark")
 
 return M
diff --git a/lua/zenbones/specs/init.lua b/lua/zenbones/specs/init.lua
index 5ad6061..b327321 100644
--- a/lua/zenbones/specs/init.lua
+++ b/lua/zenbones/specs/init.lua
@@ -10,7 +10,7 @@ local M = {}
 
 --- Get global configuration as a table.
 ---@param prefix string e.g. "zenbones"
----@param base_bg? string light or dark
+---@param base_bg string light or dark
 function M.get_global_config(prefix, base_bg)
 	if type(vim.g[prefix]) == "table" then
 		return vim.g[prefix]
@@ -44,7 +44,7 @@ function M.get_global_config(prefix, base_bg)
 			}),
 			common
 		)
-	else
+	elseif base_bg == "dark" then
 		return vim.tbl_extend(
 			"keep",
 			concat_config(prefix, {
@@ -57,6 +57,8 @@ function M.get_global_config(prefix, base_bg)
 			}),
 			common
 		)
+	else
+		error(string.format([[Invalid base_bg value: '%s', must be 'light' or 'dark'.]], base_bg))
 	end
 end
 
diff --git a/lua/zenbones/util.lua b/lua/zenbones/util.lua
index be41d69..a900695 100644
--- a/lua/zenbones/util.lua
+++ b/lua/zenbones/util.lua
@@ -12,7 +12,7 @@ end
 
 --- Auto-fill a palette with the default palette.
 ---@param p table palette
----@param base_bg? string light or dark
+---@param base_bg string light or dark
 ---@return table<string, table> palette
 function M.palette_extend(p, base_bg)
 	local lush = require "lush"
@@ -40,7 +40,7 @@ function M.palette_extend(p, base_bg)
 			sky1 = p.sky.sa(20).da(16),
 			fg1 = p.fg.li(22),
 		})
-	else
+	elseif base_bg == "dark" then
 		-- default
 		p = vim.tbl_extend("keep", p, {
 			bg = hsluv(39, 12, 9), -- sand
@@ -65,6 +65,8 @@ function M.palette_extend(p, base_bg)
 			sky1 = p.sky.sa(20).li(16),
 			fg1 = p.fg.da(22),
 		})
+	else
+		error(string.format([[Invalid base_bg value: '%s', must be 'light' or 'dark'.]], base_bg))
 	end
 end
 
diff --git a/lua/zenburned/palette.lua b/lua/zenburned/palette.lua
index b818939..7dabb3a 100644
--- a/lua/zenburned/palette.lua
+++ b/lua/zenburned/palette.lua
@@ -4,10 +4,10 @@ local hsluv = lush.hsluv
 
 local M = {}
 
-M.dark = util.palette_extend {
+M.dark = util.palette_extend({
 	bg = hsluv "#3f3f3f",
 	fg = hsluv("#efdcbc").de(14).li(20),
 	rose = hsluv "#e37170",
-}
+}, "dark")
 
 return M
diff --git a/lua/zenwritten/palette.lua b/lua/zenwritten/palette.lua
index 589d4a2..0f059e2 100644
--- a/lua/zenwritten/palette.lua
+++ b/lua/zenwritten/palette.lua
@@ -9,9 +9,9 @@ M.light = util.palette_extend({
 	fg = hsluv(0, 0, 22), -- stone
 }, "light")
 
-M.dark = util.palette_extend {
+M.dark = util.palette_extend({
 	bg = hsluv(0, 0, 9), -- sand
 	fg = hsluv(0, 0, 76), -- stone
-}
+}, "dark")
 
 return M