diff --git a/src/__tests__/blockchain-url.test.ts b/src/__tests__/blockchain-url.test.ts
new file mode 100644
index 0000000..dfafc98
--- /dev/null
+++ b/src/__tests__/blockchain-url.test.ts
@@ -0,0 +1,35 @@
+import axios from 'axios'
+import { BitgesellBlockchainSDK } from '../api'
+
+jest.mock('axios')
+
+describe('Blockchain URL construction', () => {
+  const baseAPIURL = 'https://api.bitaps.com/bgl/v1/blockchain'
+  const mockedAxiosGet = axios.get as jest.Mock
+  let bitgesellBlockchainSDK: BitgesellBlockchainSDK
+
+  beforeEach(() => {
+    mockedAxiosGet.mockResolvedValue({ data: { data: [] } })
+    bitgesellBlockchainSDK = new BitgesellBlockchainSDK({
+      baseAPIURL,
+      logger: console.log
+    })
+  })
+
+  afterEach(() => {
+    mockedAxiosGet.mockReset()
+  })
+
+  it('omits the optional block header count segment when count is not provided', async () => {
+    await bitgesellBlockchainSDK.blockchain.getBlockHeaders(10)
+
+    expect(mockedAxiosGet).toHaveBeenCalledWith(`${baseAPIURL}/block/headers/10`)
+    expect(mockedAxiosGet.mock.calls[0][0]).not.toContain('undefined')
+  })
+
+  it('includes the block header count segment when count is provided', async () => {
+    await bitgesellBlockchainSDK.blockchain.getBlockHeaders(10, 2)
+
+    expect(mockedAxiosGet).toHaveBeenCalledWith(`${baseAPIURL}/block/headers/10/2`)
+  })
+})
diff --git a/src/classes/Blockchain.ts b/src/classes/Blockchain.ts
index 70eaf2b..c01a3a9 100644
--- a/src/classes/Blockchain.ts
+++ b/src/classes/Blockchain.ts
@@ -75,7 +75,9 @@ export class Blockchain {
    * getBlockHeaders by block height
    */
   public async getBlockHeaders(blockHeight: number, count?: number): Promise<BlockHeader> {
-    const url = `${this.apiV1URL}/block/headers/${blockHeight}/${count}`
+    const url = count === undefined
+      ? `${this.apiV1URL}/block/headers/${blockHeight}`
+      : `${this.apiV1URL}/block/headers/${blockHeight}/${count}`
     const data = await this._get(url)
     return data as BlockHeader
   }
@@ -162,4 +164,4 @@ export class Blockchain {
     }
   }
 
-}
\ No newline at end of file
+}