diff --git a/__tests__/proxy.test.ts b/__tests__/proxy.test.ts
index 97cf785..1a0e28a 100644
--- a/__tests__/proxy.test.ts
+++ b/__tests__/proxy.test.ts
@@ -91,6 +91,12 @@ describe('proxy', () => {
     expect(proxyUrl).toBeDefined()
   })
 
+  it('getProxyUrl returns proxyUrl if http_proxy has no protocol', () => {
+    process.env['http_proxy'] = 'myproxysvr'
+    const proxyUrl = pm.getProxyUrl(new URL('http://github.com'))
+    expect(proxyUrl?.toString()).toBe('http://myproxysvr/')
+  })
+
   it('checkBypass returns true if host as no_proxy list', () => {
     process.env['no_proxy'] = 'myserver'
     const bypass = pm.checkBypass(new URL('https://myserver'))
diff --git a/src/proxy.ts b/src/proxy.ts
index 1a967e3..32afce6 100644
--- a/src/proxy.ts
+++ b/src/proxy.ts
@@ -14,7 +14,12 @@ export function getProxyUrl(reqUrl: URL): URL | undefined {
   })()
 
   if (proxyVar) {
-    return new URL(proxyVar)
+    try {
+      return new URL(proxyVar)
+    } catch {
+      if (!proxyVar.startsWith('http://') && !proxyVar.startsWith('https://'))
+        return new URL(`http://${proxyVar}`)
+    }
   } else {
     return undefined
   }