diff --git a/__tests__/util.test.ts b/__tests__/util.test.ts
index d19ee52f..390b696a 100644
--- a/__tests__/util.test.ts
+++ b/__tests__/util.test.ts
@@ -57,9 +57,73 @@ const {
   isCacheFeatureAvailable,
   isGhes,
   validatePaginationUrl,
-  getLatestMajorVersion
+  getLatestMajorVersion,
+  getBooleanInput
 } = await import('../src/util.js');
 
+describe('getBooleanInput', () => {
+  let inputs: Record<string, string>;
+
+  beforeEach(() => {
+    inputs = {};
+    (core.getInput as jest.Mock).mockImplementation(
+      (name: string) => inputs[name] ?? ''
+    );
+  });
+
+  afterEach(() => {
+    jest.resetAllMocks();
+  });
+
+  it.each([
+    ['true', true],
+    ['TRUE', true],
+    ['TrUe', true],
+    [' true ', true],
+    ['false', false],
+    ['FALSE', false],
+    ['FaLsE', false],
+    [' false ', false]
+  ])('parses %j as %s', (value: string, expected: boolean) => {
+    inputs['boolean-input'] = value;
+
+    expect(getBooleanInput('boolean-input')).toBe(expected);
+  });
+
+  it.each([
+    [undefined, false],
+    [false, false],
+    [true, true]
+  ])(
+    'uses the configured default %s when the input is omitted',
+    (defaultValue: boolean | undefined, expected: boolean) => {
+      expect(getBooleanInput('boolean-input', defaultValue)).toBe(expected);
+    }
+  );
+
+  it('uses the configured default for a whitespace-only input', () => {
+    inputs['boolean-input'] = '   ';
+
+    expect(getBooleanInput('boolean-input', true)).toBe(true);
+  });
+
+  it.each([
+    'check-latest',
+    'force-download',
+    'set-default',
+    'verify-signature',
+    'overwrite-settings',
+    'show-download-progress',
+    'problem-matcher'
+  ])('rejects an invalid value for %s', inputName => {
+    inputs[inputName] = 'ture';
+
+    expect(() => getBooleanInput(inputName)).toThrow(
+      `Invalid value 'ture' for boolean input '${inputName}'. Expected 'true' or 'false'.`
+    );
+  });
+});
+
 describe('isVersionSatisfies', () => {
   it.each([
     ['x', '11.0.0', true],
diff --git a/dist/cleanup/index.js b/dist/cleanup/index.js
index 6ef805e2..b2fa7b01 100644
--- a/dist/cleanup/index.js
+++ b/dist/cleanup/index.js
@@ -97365,7 +97365,18 @@ function getTempDir() {
     return tempDirectory;
 }
 function util_getBooleanInput(inputName, defaultValue = false) {
-    return ((core.getInput(inputName) || String(defaultValue)).toUpperCase() === 'TRUE');
+    const inputValue = core.getInput(inputName);
+    const normalizedValue = inputValue.trim().toLowerCase();
+    if (!normalizedValue) {
+        return defaultValue;
+    }
+    if (normalizedValue === 'true') {
+        return true;
+    }
+    if (normalizedValue === 'false') {
+        return false;
+    }
+    throw new Error(`Invalid value '${inputValue}' for boolean input '${inputName}'. Expected 'true' or 'false'.`);
 }
 function getVersionFromToolcachePath(toolPath) {
     if (toolPath) {
diff --git a/dist/setup/index.js b/dist/setup/index.js
index ee1e3f06..0ad49eb8 100644
--- a/dist/setup/index.js
+++ b/dist/setup/index.js
@@ -128364,7 +128364,18 @@ function getTempDir() {
     return tempDirectory;
 }
 function util_getBooleanInput(inputName, defaultValue = false) {
-    return ((getInput(inputName) || String(defaultValue)).toUpperCase() === 'TRUE');
+    const inputValue = getInput(inputName);
+    const normalizedValue = inputValue.trim().toLowerCase();
+    if (!normalizedValue) {
+        return defaultValue;
+    }
+    if (normalizedValue === 'true') {
+        return true;
+    }
+    if (normalizedValue === 'false') {
+        return false;
+    }
+    throw new Error(`Invalid value '${inputValue}' for boolean input '${inputName}'. Expected 'true' or 'false'.`);
 }
 function getVersionFromToolcachePath(toolPath) {
     if (toolPath) {
diff --git a/src/util.ts b/src/util.ts
index 74b73968..8881a1e7 100644
--- a/src/util.ts
+++ b/src/util.ts
@@ -20,8 +20,21 @@ export function getTempDir() {
 }
 
 export function getBooleanInput(inputName: string, defaultValue = false) {
-  return (
-    (core.getInput(inputName) || String(defaultValue)).toUpperCase() === 'TRUE'
+  const inputValue = core.getInput(inputName);
+  const normalizedValue = inputValue.trim().toLowerCase();
+
+  if (!normalizedValue) {
+    return defaultValue;
+  }
+  if (normalizedValue === 'true') {
+    return true;
+  }
+  if (normalizedValue === 'false') {
+    return false;
+  }
+
+  throw new Error(
+    `Invalid value '${inputValue}' for boolean input '${inputName}'. Expected 'true' or 'false'.`
   );
 }