diff --git a/package.json b/package.json
index 38e4f49ab1..155ec26f7f 100644
--- a/package.json
+++ b/package.json
@@ -77,7 +77,7 @@
     "build": "node scripts/build",
     "watch": "node scripts/build --watch",
     "coverage": "npx c8 -- npm test",
-    "test": "npm run test:parser && npm run test:compiler -- --parallel && npm run test:browser && npm run test:asconfig && npm run test:transform",
+    "test": "npm run test:parser && npm run test:compiler -- --parallel && npm run test:browser && npm run test:asconfig && npm run test:transform && npm run test:utils",
     "test:parser": "node --enable-source-maps tests/parser",
     "test:compiler": "node --enable-source-maps --no-warnings tests/compiler",
     "test:browser": "node --enable-source-maps tests/browser",
@@ -85,6 +85,7 @@
     "test:transform": "npm run test:transform:esm && npm run test:transform:cjs",
     "test:transform:esm": "node bin/asc tests/compiler/empty --transform ./tests/transform/index.js --noEmit && node bin/asc tests/compiler/empty --transform ./tests/transform/simple.js --noEmit",
     "test:transform:cjs": "node bin/asc tests/compiler/empty --transform ./tests/transform/cjs/index.js --noEmit && node bin/asc tests/compiler/empty --transform ./tests/transform/cjs/simple.js --noEmit",
+    "test:utils": "node tests/cli/options.js",
     "asbuild": "npm run asbuild:debug && npm run asbuild:release",
     "asbuild:debug": "node bin/asc --config src/asconfig.json --target debug",
     "asbuild:release": "node bin/asc --config src/asconfig.json --target release",
diff --git a/tests/cli/options.js b/tests/cli/options.js
index 666a3ee2d4..1eed2763ce 100644
--- a/tests/cli/options.js
+++ b/tests/cli/options.js
@@ -2,18 +2,21 @@ import assert from "assert";
 import * as optionsUtil from "../../util/options.js";
 
 const config = {
-  "enable": {
-    "type": "S",
-    "mutuallyExclusive": "disable"
+  enable: {
+    type: "S",
+    mutuallyExclusive: "disable",
   },
-  "disable": {
-    "type": "S",
-    "mutuallyExclusive": "enable"
+  disable: {
+    type: "S",
+    mutuallyExclusive: "enable",
+  },
+  other: {
+    type: "S",
+    default: ["x"],
+  },
+  bool_input_for_string: {
+    type: "s",
   },
-  "other": {
-    "type": "S",
-    "default": ["x"]
-  }
 };
 
 // Present in both should concat
@@ -33,17 +36,21 @@ assert.deepStrictEqual(merged.enable, ["c"]);
 assert.deepStrictEqual(merged.disable, ["a", "b"]);
 
 // Populating defaults should work after the fact
-optionsUtil.addDefaults(config, merged = {});
+optionsUtil.addDefaults(config, (merged = {}));
 assert.deepStrictEqual(merged.other, ["x"]);
 
-optionsUtil.addDefaults(config, merged = { other: ["y"] });
+optionsUtil.addDefaults(config, (merged = { other: ["y"] }));
 assert.deepStrictEqual(merged.other, ["y"]);
 
+// String test
+assert.deepStrictEqual(merged.bool_input_for_string, undefined);
+merged = optionsUtil.merge(config, {}, { bool_input_for_string: false });
+assert.deepStrictEqual(merged.bool_input_for_string, undefined);
+merged = optionsUtil.merge(config, {}, { bool_input_for_string: true });
+assert.deepStrictEqual(merged.bool_input_for_string, "");
+
 // Complete usage test
-let result = optionsUtil.parse([
-  "--enable", "a",
-  "--disable", "b",
-], config, false);
+let result = optionsUtil.parse(["--enable", "a", "--disable", "b"], config, false);
 
 merged = optionsUtil.merge(config, result.options, { enable: ["b", "c"] });
 merged = optionsUtil.merge(config, merged, { disable: ["a", "d"] });
@@ -52,6 +59,3 @@ optionsUtil.addDefaults(config, merged);
 assert.deepStrictEqual(merged.enable, ["a", "c"]);
 assert.deepStrictEqual(merged.disable, ["b", "d"]);
 assert.deepStrictEqual(merged.other, ["x"]);
-
-let value = optionsUtil.sanitizeValue(false, "s");
-assert.deepStrictEqual(value, null);
\ No newline at end of file
diff --git a/util/options.d.ts b/util/options.d.ts
index aa153a7483..facc36d622 100644
--- a/util/options.d.ts
+++ b/util/options.d.ts
@@ -68,6 +68,3 @@ export function resolvePath(path: string, baseDir: string, useNodeResolution?: b
 
 /** Populates default values on a parsed options result. */
 export function addDefaults(config: Config, options: OptionSet): void;
-
-/** Sanitizes an option value to be a valid value of the option's type. */
-export function sanitizeValue(value: any, type: string): boolean | number | string | null | number[] | string[]; // eslint-disable-line @typescript-eslint/no-explicit-any
\ No newline at end of file
diff --git a/util/options.js b/util/options.js
index 40132fe155..251b9f3924 100644
--- a/util/options.js
+++ b/util/options.js
@@ -141,7 +141,7 @@ export function help(config, options) {
 }
 
 /** Sanitizes an option value to be a valid value of the option's type. */
-export function sanitizeValue(value, type) {
+function sanitizeValue(value, type) {
   if (value != null) {
     switch (type) {
       case undefined: