diff --git a/toolkit/components/telemetry/tests/unit/test_ChildHistograms.js b/toolkit/components/telemetry/tests/unit/test_ChildHistograms.js
index d02ac1333200..4233328b600f 100644
--- a/toolkit/components/telemetry/tests/unit/test_ChildHistograms.js
+++ b/toolkit/components/telemetry/tests/unit/test_ChildHistograms.js
@@ -2,7 +2,6 @@
 Cu.import("resource://gre/modules/TelemetryController.jsm", this);
 Cu.import("resource://gre/modules/TelemetrySession.jsm", this);
 Cu.import("resource://gre/modules/PromiseUtils.jsm", this);
-Cu.import("resource://testing-common/ContentTaskUtils.jsm", this);
 
 const MESSAGE_TELEMETRY_PAYLOAD = "Telemetry:Payload";
 const MESSAGE_TELEMETRY_GET_CHILD_PAYLOAD = "Telemetry:GetChildPayload";
@@ -28,6 +27,10 @@ function run_child_test() {
   countKeyed.add("a");
   countKeyed.add("b");
   countKeyed.add("b");
+
+  // Check payload values.
+  const payload = TelemetrySession.getPayload("test-ping");
+  check_histogram_values(payload);
 }
 
 function check_histogram_values(payload) {
@@ -58,6 +61,8 @@ add_task(function*() {
     run_child_test();
     dump("... done with child test\n");
     do_send_remote_message(MESSAGE_CHILD_TEST_DONE);
+    dump("... waiting for child payload collection\n");
+    yield do_await_remote_message(MESSAGE_TELEMETRY_GET_CHILD_PAYLOAD);
     return;
   }
 
@@ -75,20 +80,20 @@ add_task(function*() {
   let childPromise = run_test_in_child("test_ChildHistograms.js");
   yield do_await_remote_message(MESSAGE_CHILD_TEST_DONE);
 
-  yield ContentTaskUtils.waitForCondition(() => {
-    let payload = TelemetrySession.getPayload("test-ping");
-    return payload &&
-           "processes" in payload &&
-           "content" in payload.processes &&
-           "histograms" in payload.processes.content &&
-           "TELEMETRY_TEST_COUNT" in payload.processes.content.histograms;
-  });
+  // Gather payload from child.
+  dump("... requesting child payloads\n");
+  let promiseMessage = do_await_remote_message(MESSAGE_TELEMETRY_PAYLOAD);
+  TelemetrySession.requestChildPayloads();
+  yield promiseMessage;
+  dump("... received child payload\n");
+
+  // Check child payload.
   const payload = TelemetrySession.getPayload("test-ping");
-  Assert.ok("processes" in payload, "Should have processes section");
-  Assert.ok("content" in payload.processes,"Should have child process section");
-  Assert.ok("histograms" in payload.processes.content, "Child process section should have histograms.");
-  Assert.ok("keyedHistograms" in payload.processes.content, "Child process section should have keyed histograms.");
-  check_histogram_values(payload.processes.content);
+  Assert.ok("childPayloads" in payload, "Should have child payloads.");
+  Assert.equal(payload.childPayloads.length, 1, "Should have received one child payload so far.");
+  Assert.ok("histograms" in payload.childPayloads[0], "Child payload should have histograms.");
+  Assert.ok("keyedHistograms" in payload.childPayloads[0], "Child payload should have keyed histograms.");
+  check_histogram_values(payload.childPayloads[0]);
 
   do_test_finished();
 });