diff --git a/R/inputs.R b/R/inputs.R
index 7a9ae40..8075519 100644
--- a/R/inputs.R
+++ b/R/inputs.R
@@ -129,7 +129,7 @@ build_dropdown_extra_choices <- function(choices) {
   if (length(choices) == 0) {
     choices_js <- ""
   } else {
-    choices_js <- paste0(", choices: ", rjson::toJSON(choices))
+    choices_js <- paste0(", choices: ", rjson::toJSON(as.list(choices)))
   }
 
   return(choices_js)
diff --git a/tests/testthat/test-inputs.R b/tests/testthat/test-inputs.R
index 65e5965..d7b2d84 100644
--- a/tests/testthat/test-inputs.R
+++ b/tests/testthat/test-inputs.R
@@ -34,6 +34,12 @@ test_that("`dropdown_extra` sets choices to blank when length is 0", {
   expect_equal(choices, "")
 })
 
+test_that("`dropdown_extra` serializes a single value as an array", {
+  choices <- build_dropdown_extra_choices("a")
+
+  expect_equal(choices, ', choices: ["a"]')
+})
+
 test_that("`dropdown_extra` sets choices correctly", {
   choices <- build_dropdown_extra_choices(letters[1:3])