diff --git a/R/standalone-checks.R b/R/standalone-checks.R
index 0d19387..ce1ab36 100644
--- a/R/standalone-checks.R
+++ b/R/standalone-checks.R
@@ -12,6 +12,9 @@
 #
 # ## Changelog
 #
+# 2026-08-10
+#   - Updated `check_scalar()` to return an error for lists of length 1.
+#
 # 2026-07-01
 #   - `check_*()` functions now error on empty input when `allow_empty = FALSE`
 #     (previously empty input silently passed class/type checks) (#30)
@@ -20,6 +23,7 @@
 #
 # 2025-05-08
 #   - Added `check_identical()` and `check_identical_length()`
+#
 # 2025-04-27
 #   - Added `check_named()`
 
@@ -256,18 +260,27 @@ check_scalar <- function(x,
                          message =
                            ifelse(
                              allow_empty,
-                             "The {.arg {arg_name}} argument must be length {.val {1}} or empty.",
-                             "The {.arg {arg_name}} argument must be length {.val {1}}."
+                             "The {.arg {arg_name}} argument must be a vector of length {.val {1}} or empty.",
+                             "The {.arg {arg_name}} argument must be a vector of length {.val {1}}."
                            ),
                          arg_name = rlang::caller_arg(x),
                          class = "check_scalar",
                          call = get_cli_abort_call(),
                          envir = rlang::current_env()) {
-  check_length(
-    x = x, length = 1L, message = message,
-    allow_empty = allow_empty, arg_name = arg_name,
-    class = class, call = call, envir = envir
-  )
+  # if empty: return invisibly when allowed, otherwise error
+  if (rlang::is_empty(x)) {
+    if (isTRUE(allow_empty)) {
+      return(invisible(x))
+    }
+    cli::cli_abort(message, class = c(class, "standalone-checks"), call = call, .envir = envir)
+  }
+
+  # input must be a vector of length 1 (not a list)
+  if (length(x) != 1L || is.list(x)) {
+    cli::cli_abort(message, class = c(class, "standalone-checks"), call = call, .envir = envir)
+  }
+
+  invisible(x)
 }
 
 #' Check Number of Levels
diff --git a/tests/testthat/_snaps/standalone-checks.md b/tests/testthat/_snaps/standalone-checks.md
index 3893753..a17d484 100644
--- a/tests/testthat/_snaps/standalone-checks.md
+++ b/tests/testthat/_snaps/standalone-checks.md
@@ -60,7 +60,7 @@
       myfunc(c(TRUE, FALSE))
     Condition
       Error in `myfunc()`:
-      ! The `x` argument must be length 1.
+      ! The `x` argument must be a vector of length 1.
 
 ---
 
diff --git a/tests/testthat/test-standalone-checks.R b/tests/testthat/test-standalone-checks.R
index e5ec198..6f666be 100644
--- a/tests/testthat/test-standalone-checks.R
+++ b/tests/testthat/test-standalone-checks.R
@@ -106,7 +106,13 @@ test_that("check functions work", {
 
   expect_error(
     check_scalar(c(1, 10)),
-    "The `c(1, 10)` argument must be length 1.",
+    "The `c(1, 10)` argument must be a vector of length 1.",
+    fixed = TRUE
+  )
+
+  expect_error(
+    check_scalar(list(1)),
+    "The `list(1)` argument must be a vector of length 1.",
     fixed = TRUE
   )