diff --git a/.github/workflows/CI.yml b/.github/workflows/CI.yml
index a46551c..dc3d3b7 100644
--- a/.github/workflows/CI.yml
+++ b/.github/workflows/CI.yml
@@ -206,7 +206,7 @@ jobs:
           RUSTUP_IO_THREADS: 1
         with:
           operating_system: freebsd
-          version: '14.0'
+          version: '14.1'
           memory: 8G
           cpu_count: 3
           environment_variables: 'DEBUG RUSTUP_IO_THREADS'
@@ -257,6 +257,7 @@ jobs:
         node:
           - '18'
           - '20'
+          - '22'
         transform_all:
           - 'true'
           - 'false'
@@ -307,6 +308,7 @@ jobs:
         node:
           - '18'
           - '20'
+          - '22'
         exclude:
           # too slow
           - target: aarch64-unknown-linux-gnu
diff --git a/packages/core/index.d.ts b/packages/core/index.d.ts
index 9455638..2ed11e9 100644
--- a/packages/core/index.d.ts
+++ b/packages/core/index.d.ts
@@ -23,7 +23,7 @@ export interface LoadContext {
   /** Export conditions of the relevant `package.json` */
   conditions?: Array<string>
   /** The format optionally supplied by the `resolve` hook chain */
-  format: string
+  format: string | null
   /** An object whose key-value pairs represent the assertions for the module to import */
   importAttributes: Record<string, string>
 }
diff --git a/src/lib.rs b/src/lib.rs
index bea0277..5479c92 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -464,7 +464,7 @@ pub struct LoadContext {
     /// Export conditions of the relevant `package.json`
     pub conditions: Option<Vec<String>>,
     /// The format optionally supplied by the `resolve` hook chain
-    pub format: String,
+    pub format: Either<String, Null>,
     /// An object whose key-value pairs represent the assertions for the module to import
     pub import_attributes: HashMap<String, String>,
 }
@@ -487,11 +487,12 @@ pub fn load(
     >,
 ) -> Result<Either<LoadFnOutput, PromiseRaw<LoadFnOutput>>> {
     tracing::debug!(url = ?url, context = ?context, "load");
-    if url.starts_with("data:")
-        || context.format == "builtin"
-        || context.format == "json"
-        || context.format == "wasm"
-    {
+    if url.starts_with("data:") || {
+        match context.format {
+            Either::A(ref format) => format == "builtin" || format == "json" || format == "wasm",
+            _ => true,
+        }
+    } {
         tracing::debug!("short-circuiting load: {}", url);
         return next_load.call((url, Some(context)));
     }