diff --git a/src/common/framework/params_utils.ts b/src/common/framework/params_utils.ts
index e8c9f4cedda5..8292e4533edf 100644
--- a/src/common/framework/params_utils.ts
+++ b/src/common/framework/params_utils.ts
@@ -2,10 +2,20 @@ import { comparePublicParamsPaths, Ordering } from './query/compare.js';
 import { kWildcard, kParamSeparator, kParamKVSeparator } from './query/separators.js';
 
 // Consider adding more types here if needed
-export type ParamArgument = void | undefined | number | string | boolean | number[];
-export interface CaseParams {
+//
+// TODO: This type isn't actually used to constrain what you're allowed to do in `.params()`, so
+// it's not really serving its purpose. Figure out how to fix that?
+export type ParamArgument =
+  | undefined
+  | null
+  | number
+  | string
+  | boolean
+  | number[]
+  | { readonly [k: string]: undefined | null | number | string | boolean };
+export type CaseParams = {
   readonly [k: string]: ParamArgument;
-}
+};
 export interface CaseParamsRW {
   [k: string]: ParamArgument;
 }
diff --git a/src/common/framework/query/encode_selectively.ts b/src/common/framework/query/encode_selectively.ts
index 38bbaf02a81e..ab1997b6e458 100644
--- a/src/common/framework/query/encode_selectively.ts
+++ b/src/common/framework/query/encode_selectively.ts
@@ -16,6 +16,8 @@ export function encodeURIComponentSelectively(s: string): string {
   ret = ret.replace(/%3D/g, '='); // for params (k=v)
   ret = ret.replace(/%5B/g, '['); // for JSON arrays
   ret = ret.replace(/%5D/g, ']'); // for JSON arrays
+  ret = ret.replace(/%7B/g, '{'); // for JSON objects
+  ret = ret.replace(/%7D/g, '}'); // for JSON objects
   ret = ret.replace(/%E2%9C%97/g, '✗'); // for jsUndefinedMagicValue
   return ret;
 }
diff --git a/src/common/framework/query/parseQuery.ts b/src/common/framework/query/parseQuery.ts
index b8834421dd33..bcbb23e86b8e 100644
--- a/src/common/framework/query/parseQuery.ts
+++ b/src/common/framework/query/parseQuery.ts
@@ -30,9 +30,29 @@ function parseQueryImpl(s: string): TestQuery {
   // Undo encodeURIComponentSelectively
   s = decodeURIComponent(s);
 
-  // bigParts are: suite, group, test, params (note kBigSeparator could appear in params)
-  const [suite, fileString, testString, paramsString] = s.split(kBigSeparator, 4);
-  assert(fileString !== undefined, `filter string must have at least one ${kBigSeparator}`);
+  // bigParts are: suite, file, test, params (note kBigSeparator could appear in params)
+  let suite: string;
+  let fileString: string | undefined;
+  let testString: string | undefined;
+  let paramsString: string | undefined;
+  {
+    const i1 = s.indexOf(kBigSeparator);
+    assert(i1 !== -1, `query string must have at least one ${kBigSeparator}`);
+    suite = s.substring(0, i1);
+    const i2 = s.indexOf(kBigSeparator, i1 + 1);
+    if (i2 === -1) {
+      fileString = s.substring(i1 + 1);
+    } else {
+      fileString = s.substring(i1 + 1, i2);
+      const i3 = s.indexOf(kBigSeparator, i2 + 1);
+      if (i3 === -1) {
+        testString = s.substring(i2 + 1);
+      } else {
+        testString = s.substring(i2 + 1, i3);
+        paramsString = s.substring(i3 + 1);
+      }
+    }
+  }
 
   const { parts: file, wildcard: filePathHasWildcard } = parseBigPart(fileString, kPathSeparator);
 
diff --git a/src/demo/json.spec.ts b/src/demo/json.spec.ts
new file mode 100644
index 000000000000..84cbf0c8054b
--- /dev/null
+++ b/src/demo/json.spec.ts
@@ -0,0 +1,10 @@
+export const description = 'Description for a.spec.ts';
+
+import { makeTestGroup } from '../common/framework/test_group.js';
+import { UnitTest } from '../unittests/unit_test.js';
+
+export const g = makeTestGroup(UnitTest);
+
+g.test('json')
+  .params([{ p: { x: 1, y: 'two' } }])
+  .fn(() => {});
diff --git a/src/unittests/url_query.spec.ts b/src/unittests/url_query.spec.ts
index 1a9e8fc3aaf5..c3908596cf8d 100644
--- a/src/unittests/url_query.spec.ts
+++ b/src/unittests/url_query.spec.ts
@@ -27,10 +27,20 @@ g.test('stringifyQuery,single_case').fn(t => {
     new TestQuerySingleCase('a', ['b_1', '2_c'], ['d_3', '4_e'], {
       f: 'g',
       _pri1: 0,
-      a: 3,
+      x: 3,
       _pri2: 1,
     }),
-    'a:b_1,2_c:d_3,4_e:f="g";a=3'
+    'a:b_1,2_c:d_3,4_e:f="g";x=3'
+  );
+});
+
+g.test('stringifyQuery,single_case,json').fn(t => {
+  t.expectQueryString(
+    new TestQuerySingleCase('a', ['b_1', '2_c'], ['d_3', '4_e'], {
+      f: 'g',
+      x: { p: 2, q: 'Q' },
+    }),
+    'a:b_1,2_c:d_3,4_e:f="g";x={"p":2,"q":"Q"}'
   );
 });