diff --git a/scripts/test b/scripts/test
new file mode 100755
index 0000000..4fc9525
--- /dev/null
+++ b/scripts/test
@@ -0,0 +1,6 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+echo "Running regression tests..."
+
+lua test/regression/uncurried.lua
diff --git a/src/Effect/Uncurried.lua b/src/Effect/Uncurried.lua
index 11de067..01acec5 100644
--- a/src/Effect/Uncurried.lua
+++ b/src/Effect/Uncurried.lua
@@ -196,7 +196,7 @@ return {
                     return function(i)
                       return function(j)
                         return function()
-                          return fn(a, b, c, d, e, f, g, h, i)
+                          return fn(a, b, c, d, e, f, g, h, i, j)
                         end
                       end
                     end
diff --git a/test/regression/uncurried.lua b/test/regression/uncurried.lua
new file mode 100644
index 0000000..3e0eb09
--- /dev/null
+++ b/test/regression/uncurried.lua
@@ -0,0 +1,25 @@
+-- Regression guard: runEffectFn10 must forward all ten arguments.
+--
+-- The FFI bound ten curried parameters a..j but called the underlying
+-- function with only nine (a..i), silently dropping j. This loads the
+-- FFI table directly and checks that every argument reaches `fn`.
+
+local M = assert(dofile("src/Effect/Uncurried.lua"))
+
+local seen
+local recorder = function(...)
+  seen = { ... }
+  return nil
+end
+
+-- runEffectFn10(fn)(a)(b)...(j)() applies fn to all ten arguments.
+M.runEffectFn10(recorder)(1)(2)(3)(4)(5)(6)(7)(8)(9)(10)()
+
+assert(seen ~= nil, "fn was never called")
+assert(#seen == 10, "expected 10 forwarded arguments, got " .. #seen)
+for k = 1, 10 do
+  assert(seen[k] == k,
+    "argument #" .. k .. " not forwarded (got " .. tostring(seen[k]) .. ")")
+end
+
+print("OK runEffectFn10 forwards all ten arguments")