diff --git a/.changeset/stale-onions-check.md b/.changeset/stale-onions-check.md
new file mode 100644
index 0000000000..733b757af2
--- /dev/null
+++ b/.changeset/stale-onions-check.md
@@ -0,0 +1,5 @@
+---
+'@urql/core': patch
+---
+
+Fix stringifyVariables breaking on x.toJSON scalars.
diff --git a/packages/core/src/utils/stringifyVariables.test.ts b/packages/core/src/utils/stringifyVariables.test.ts
index 6e6c6ae486..2d592e4e86 100644
--- a/packages/core/src/utils/stringifyVariables.test.ts
+++ b/packages/core/src/utils/stringifyVariables.test.ts
@@ -29,7 +29,7 @@ it('returns null for circular structures', () => {
 
 it('stringifies dates correctly', () => {
   const date = new Date('2019-12-11T04:20:00');
-  expect(stringifyVariables(date)).toBe(date.toJSON());
+  expect(stringifyVariables(date)).toBe(`"${date.toJSON()}"`);
 });
 
 it('stringifies dictionaries (Object.create(null)) correctly', () => {
diff --git a/packages/core/src/utils/stringifyVariables.ts b/packages/core/src/utils/stringifyVariables.ts
index 493cb42c08..d8ce554e69 100644
--- a/packages/core/src/utils/stringifyVariables.ts
+++ b/packages/core/src/utils/stringifyVariables.ts
@@ -7,7 +7,7 @@ const stringify = (x: any): string => {
   } else if (typeof x !== 'object') {
     return JSON.stringify(x) || '';
   } else if (x.toJSON) {
-    return x.toJSON();
+    return stringify(x.toJSON());
   } else if (Array.isArray(x)) {
     let out = '[';
     for (let i = 0, l = x.length; i < l; i++) {