diff --git a/__tests__/branch.test.ts b/__tests__/branch.test.ts
index 5252b508..0fcacb41 100644
--- a/__tests__/branch.test.ts
+++ b/__tests__/branch.test.ts
@@ -23,13 +23,6 @@ describe('getBranchName', () => {
       expect(result).toEqual('head-branch-name');
     });
   });
-
-  describe('when no branch is specified', () => {
-    it('returns the head branch name', () => {
-      const result = getBranchName();
-      expect(result).toEqual('head-branch-name');
-    });
-  });
 });
 
 describe('checkBranch', () => {
@@ -45,14 +38,14 @@ describe('checkBranch', () => {
   describe('when a single pattern is provided', () => {
     describe('and the pattern matches the head branch', () => {
       it('returns true', () => {
-        const result = checkBranch(['^test']);
+        const result = checkBranch(['^test'], 'head');
         expect(result).toBe(true);
       });
     });
 
     describe('and the pattern does not match the head branch', () => {
       it('returns false', () => {
-        const result = checkBranch(['^feature/']);
+        const result = checkBranch(['^feature/'], 'head');
         expect(result).toBe(false);
       });
     });
@@ -61,21 +54,21 @@ describe('checkBranch', () => {
   describe('when multiple patterns are provided', () => {
     describe('and at least one pattern matches', () => {
       it('returns true', () => {
-        const result = checkBranch(['^test/', '^feature/']);
+        const result = checkBranch(['^test/', '^feature/'], 'head');
         expect(result).toBe(true);
       });
     });
 
     describe('and all patterns match', () => {
       it('returns true', () => {
-        const result = checkBranch(['^test/', '/feature/']);
+        const result = checkBranch(['^test/', '/feature/'], 'head');
         expect(result).toBe(true);
       });
     });
 
     describe('and no patterns match', () => {
       it('returns false', () => {
-        const result = checkBranch(['^feature/', '/test$']);
+        const result = checkBranch(['^feature/', '/test$'], 'head');
         expect(result).toBe(false);
       });
     });
diff --git a/src/branch.ts b/src/branch.ts
index c177d24a..6759b05e 100644
--- a/src/branch.ts
+++ b/src/branch.ts
@@ -35,7 +35,7 @@ export function toBranchMatchConfig(config: any): BranchMatchConfig {
   return branchConfig;
 }
 
-export function getBranchName(branchBase?: BranchBase): string | undefined {
+export function getBranchName(branchBase: BranchBase): string | undefined {
   const pullRequest = github.context.payload.pull_request;
   if (!pullRequest) {
     return undefined;
@@ -50,7 +50,7 @@ export function getBranchName(branchBase?: BranchBase): string | undefined {
 
 export function checkBranch(
   regexps: string[],
-  branchBase?: BranchBase
+  branchBase: BranchBase
 ): boolean {
   const branchName = getBranchName(branchBase);
   if (!branchName) {