--- a/toolkit/components/telemetry/tests/gtest/TestScalars.cpp
+++ b/toolkit/components/telemetry/tests/gtest/TestScalars.cpp
@@ -311,8 +311,62 @@ TEST_F(TelemetryTestFixture, ScalarEvent
   // Check the recorded value.
   JS::RootedValue scalarsSnapshot(cx.GetJSContext());
   GetScalarsSnapshot(true, cx.GetJSContext(), &scalarsSnapshot, ProcessID::Dynamic);
 
   // Recording in parent or content doesn't matter for dynamic scalars
   // which all end up in the same place.
   CheckKeyedUintScalar(kScalarName, kLongestEvent, cx.GetJSContext(), scalarsSnapshot, 2);
 }
+
+TEST_F(TelemetryTestFixture, WrongScalarOperator) {
+  AutoJSContextWithGlobal cx(mCleanGlobal);
+
+  // Make sure we don't get scalars from other tests.
+  Unused << mTelemetry->ClearScalars();
+
+  Telemetry::ScalarSet(Telemetry::ScalarID::TELEMETRY_TEST_STRING_KIND, NS_LITERAL_STRING(EXPECTED_STRING));
+  Telemetry::ScalarSet(Telemetry::ScalarID::TELEMETRY_TEST_BOOLEAN_KIND, true);
+
+  TelemetryScalar::DeserializationStarted();
+
+  Telemetry::ScalarAdd(Telemetry::ScalarID::TELEMETRY_TEST_STRING_KIND, 1447);
+  Telemetry::ScalarAdd(Telemetry::ScalarID::TELEMETRY_TEST_BOOLEAN_KIND, 1447);
+  TelemetryScalar::ApplyPendingOperations();
+
+  JS::RootedValue scalarsSnapshot(cx.GetJSContext());
+  GetScalarsSnapshot(false, cx.GetJSContext(), &scalarsSnapshot);
+  CheckStringScalar("telemetry.test.string_kind", cx.GetJSContext(), scalarsSnapshot, EXPECTED_STRING);
+  CheckBoolScalar("telemetry.test.boolean_kind", cx.GetJSContext(), scalarsSnapshot, true);
+}
+
+TEST_F(TelemetryTestFixture, WrongKeyedScalarOperator) {
+
+  AutoJSContextWithGlobal cx(mCleanGlobal);
+
+  // Make sure we don't get scalars from other tests.
+  Unused << mTelemetry->ClearScalars();
+
+
+  const uint32_t kExpectedUint = 1172017;
+
+  Telemetry::ScalarSet(Telemetry::ScalarID::TELEMETRY_TEST_KEYED_UNSIGNED_INT,
+                       NS_LITERAL_STRING("key1"), kExpectedUint);
+  Telemetry::ScalarSet(Telemetry::ScalarID::TELEMETRY_TEST_KEYED_BOOLEAN_KIND,
+                       NS_LITERAL_STRING("key2"), true);
+
+  TelemetryScalar::DeserializationStarted();
+
+  Telemetry::ScalarSet(Telemetry::ScalarID::TELEMETRY_TEST_KEYED_UNSIGNED_INT,
+                       NS_LITERAL_STRING("key1"), false);
+  Telemetry::ScalarSet(Telemetry::ScalarID::TELEMETRY_TEST_KEYED_BOOLEAN_KIND,
+                       NS_LITERAL_STRING("key2"), static_cast<uint32_t>(13));
+
+  TelemetryScalar::ApplyPendingOperations();
+
+  JS::RootedValue scalarsSnapshot(cx.GetJSContext());
+  GetScalarsSnapshot(true, cx.GetJSContext(), &scalarsSnapshot);
+  CheckKeyedUintScalar("telemetry.test.keyed_unsigned_int", "key1",
+                       cx.GetJSContext(), scalarsSnapshot, kExpectedUint);
+  CheckKeyedBoolScalar("telemetry.test.keyed_boolean_kind", "key2",
+                       cx.GetJSContext(), scalarsSnapshot, true);
+
+}