diff --git a/scripts/test b/scripts/test
new file mode 100755
index 0000000..03cfc1a
--- /dev/null
+++ b/scripts/test
@@ -0,0 +1,6 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+echo "Running regression tests..."
+
+lua test/regression/format.lua
diff --git a/src/Data/Number/Format.lua b/src/Data/Number/Format.lua
index c109e45..137653d 100644
--- a/src/Data/Number/Format.lua
+++ b/src/Data/Number/Format.lua
@@ -1,6 +1,6 @@
 return {
-  toPrecisionNative = (function(d) return function(n) return string.format("%." .. tostring(d) .. "f", number) end end),
-  toFixedNative = (function(d) return function(n) return string.format("%." .. tostring(d) .. "d", number) end end),
-  toExponentialNative = (function(d) return function(n) return string.format("%." .. tostring(d) .. "e", number) end end),
+  toPrecisionNative = (function(d) return function(n) return string.format("%." .. tostring(d) .. "f", n) end end),
+  toFixedNative = (function(d) return function(n) return string.format("%." .. tostring(d) .. "d", n) end end),
+  toExponentialNative = (function(d) return function(n) return string.format("%." .. tostring(d) .. "e", n) end end),
   toString = (function(num) return tostring(num) end)
 }
diff --git a/test/regression/format.lua b/test/regression/format.lua
new file mode 100644
index 0000000..0fb2d6d
--- /dev/null
+++ b/test/regression/format.lua
@@ -0,0 +1,8 @@
+-- Regression guard: Format.lua must use its bound argument n, not an
+-- unbound `number` global (nil at runtime, which made every formatter error).
+local M = assert(dofile("src/Data/Number/Format.lua"))
+
+assert(type(M.toPrecisionNative(6)(1234.56789)) == "string",
+  "toPrecisionNative must format its bound argument, not error on a nil global")
+
+print("OK Format.lua uses the bound argument n")