diff --git a/packages/fresh/src/jsonify/__snapshots__/round_trip_test.ts.snap b/packages/fresh/src/jsonify/__snapshots__/round_trip_test.ts.snap
index f7f4f3716c8..ae21ba2af00 100644
--- a/packages/fresh/src/jsonify/__snapshots__/round_trip_test.ts.snap
+++ b/packages/fresh/src/jsonify/__snapshots__/round_trip_test.ts.snap
@@ -44,6 +44,8 @@ snapshot[`round trip - URL {\\n  href: 'https://fresh.deno.dev/',\\n  origin: 'h
 
 snapshot[`round trip - 1990-05-31T00:00:00.000Z 1`] = `'[["Date","1990-05-31T00:00:00.000Z"]]'`;
 
+snapshot[`round trip - Invalid Date 1`] = `'[["Date","Invalid Date"]]'`;
+
 snapshot[`round trip - Map(2) { 1 => null, undefined => -2 } 1`] = `'[["Map",[1,-2,-1,2]],1,-2]'`;
 
 snapshot[`round trip - Set(5) { 1, 2, null, -2, NaN } 1`] = `'[["Set",[1,2,-2,3,-3]],1,2,-2]'`;
diff --git a/packages/fresh/src/jsonify/round_trip_test.ts b/packages/fresh/src/jsonify/round_trip_test.ts
index 83e11108c73..c44e5f9bad0 100644
--- a/packages/fresh/src/jsonify/round_trip_test.ts
+++ b/packages/fresh/src/jsonify/round_trip_test.ts
@@ -34,6 +34,7 @@ const TESTS = [
   new Uint8Array([1, 2, 3]),
   new URL("https://fresh.deno.dev"),
   new Date("1990-05-31"),
+  new Date("Invalid Date"),
   new Map([[1, null], [undefined, -2]]),
   new Set([1, 2, null, -2, NaN]),
   [1, , 3],
diff --git a/packages/fresh/src/jsonify/stringify.ts b/packages/fresh/src/jsonify/stringify.ts
index 1179b5a3cde..00231115f73 100644
--- a/packages/fresh/src/jsonify/stringify.ts
+++ b/packages/fresh/src/jsonify/stringify.ts
@@ -108,7 +108,13 @@ function serializeInner(
     if (value instanceof URL) {
       str += `["URL","${value.href}"]`;
     } else if (value instanceof Date) {
-      str += `["Date","${value.toISOString()}"]`;
+      let iso: string;
+      try {
+        iso = value.toISOString();
+      } catch {
+        iso = "Invalid Date";
+      }
+      str += `["Date","${iso}"]`;
     } else if (value instanceof RegExp) {
       str += `["RegExp",${JSON.stringify(value.source)}, "${value.flags}"]`;
     } else if (value instanceof Uint8Array) {