diff --git a/lib/entry-points.js b/lib/entry-points.js
index 40188eb2d..48a157aa6 100644
--- a/lib/entry-points.js
+++ b/lib/entry-points.js
@@ -151429,12 +151429,13 @@ function parseUserConfig(logger, pathInput, contents, validateConfig) {
 }
 
 // src/config/remote-file.ts
+var DEFAULT_CONFIG_FILE_REF = "main";
 function parseRemoteFileAddress(configFile) {
   const format = new RegExp(
-    "(?<owner>[^/]+)/(?<repo>[^/]+)/(?<path>[^@]+)@(?<ref>.*)"
+    "(?<owner>[^/]+)/(?<repo>[^/]+)/(?<path>[^@]+)(@(?<ref>.*))?"
   );
   const pieces = format.exec(configFile);
-  if (pieces?.groups === void 0 || pieces.length < 5) {
+  if (!pieces?.groups?.owner || !pieces?.groups?.repo || !pieces?.groups?.path) {
     throw new ConfigurationError(
       getConfigFileRepoFormatInvalidMessage(configFile)
     );
@@ -151443,7 +151444,7 @@ function parseRemoteFileAddress(configFile) {
     owner: pieces.groups.owner,
     repo: pieces.groups.repo,
     path: pieces.groups.path,
-    ref: pieces.groups.ref
+    ref: pieces.groups.ref || DEFAULT_CONFIG_FILE_REF
   };
 }
 
diff --git a/src/config/remote-file.test.ts b/src/config/remote-file.test.ts
index fe8589d94..d45c2ec6d 100644
--- a/src/config/remote-file.test.ts
+++ b/src/config/remote-file.test.ts
@@ -2,7 +2,11 @@ import test from "ava";
 
 import { ConfigurationError } from "../util";
 
-import { parseRemoteFileAddress, RemoteFileAddress } from "./remote-file";
+import {
+  DEFAULT_CONFIG_FILE_REF,
+  parseRemoteFileAddress,
+  RemoteFileAddress,
+} from "./remote-file";
 
 test("expandConfigFileInput accepts full remote addresses", async (t) => {
   t.deepEqual(parseRemoteFileAddress("owner/repo/path@ref"), {
@@ -23,6 +27,22 @@ test("expandConfigFileInput accepts full remote addresses", async (t) => {
   );
 });
 
+test("expandConfigFileInput accepts remote address without a ref", async (t) => {
+  t.deepEqual(parseRemoteFileAddress("owner/repo/path"), {
+    owner: "owner",
+    repo: "repo",
+    path: "path",
+    ref: DEFAULT_CONFIG_FILE_REF,
+  } satisfies RemoteFileAddress);
+
+  t.deepEqual(parseRemoteFileAddress("owner/repo/path@"), {
+    owner: "owner",
+    repo: "repo",
+    path: "path",
+    ref: DEFAULT_CONFIG_FILE_REF,
+  } satisfies RemoteFileAddress);
+});
+
 test("expandConfigFileInput rejects invalid values", async (t) => {
   t.throws(() => parseRemoteFileAddress("  "), {
     instanceOf: ConfigurationError,
diff --git a/src/config/remote-file.ts b/src/config/remote-file.ts
index 66328586f..9ab89ad4a 100644
--- a/src/config/remote-file.ts
+++ b/src/config/remote-file.ts
@@ -13,6 +13,9 @@ export interface RemoteFileAddress {
   ref: string;
 }
 
+/** The default ref to use in configuration file shorthands. */
+export const DEFAULT_CONFIG_FILE_REF = "main";
+
 /**
  * Attempts to parse `configFile` into an array of `RemoteFileAddress` components.
  *
@@ -23,12 +26,16 @@ export interface RemoteFileAddress {
 export function parseRemoteFileAddress(configFile: string): RemoteFileAddress {
   // retrieve the various parts of the config location, and ensure they're present
   const format = new RegExp(
-    "(?<owner>[^/]+)/(?<repo>[^/]+)/(?<path>[^@]+)@(?<ref>.*)",
+    "(?<owner>[^/]+)/(?<repo>[^/]+)/(?<path>[^@]+)(@(?<ref>.*))?",
   );
   const pieces = format.exec(configFile);
 
-  // 5 = 4 groups + the whole expression
-  if (pieces?.groups === undefined || pieces.length < 5) {
+  // Check that the regular expression matched and that we have at least the required components.
+  if (
+    !pieces?.groups?.owner ||
+    !pieces?.groups?.repo ||
+    !pieces?.groups?.path
+  ) {
     throw new ConfigurationError(
       errorMessages.getConfigFileRepoFormatInvalidMessage(configFile),
     );
@@ -38,6 +45,6 @@ export function parseRemoteFileAddress(configFile: string): RemoteFileAddress {
     owner: pieces.groups.owner,
     repo: pieces.groups.repo,
     path: pieces.groups.path,
-    ref: pieces.groups.ref,
+    ref: pieces.groups.ref || DEFAULT_CONFIG_FILE_REF,
   };
 }