diff --git a/content/media/AudioEventTimeline.h b/content/media/AudioEventTimeline.h
index dff1871c147..e42b670ecff 100644
--- a/content/media/AudioEventTimeline.h
+++ b/content/media/AudioEventTimeline.h
@@ -249,22 +249,7 @@ public:
 
     // If the requested time is before all of the existing events
     if (!previous) {
-      switch (next->mType) {
-      case AudioTimelineEvent::SetValue:
-      case AudioTimelineEvent::SetTarget:
-        // The requested time is before the first event
-        return mValue;
-      case AudioTimelineEvent::LinearRamp:
-        // Use t=0 as T0 and v=defaultValue as V0
-        return LinearInterpolate(0.0, mValue, next->template Time<TimeType>(), next->mValue, aTime);
-      case AudioTimelineEvent::ExponentialRamp:
-        // Use t=0 as T0 and v=defaultValue as V0
-        return ExponentialInterpolate(0.0, mValue, next->template Time<TimeType>(), next->mValue, aTime);
-      case AudioTimelineEvent::SetValueCurve:
-        // TODO: implement
-        return 0.0f;
-      }
-      MOZ_ASSERT(false, "unreached");
+      return mValue;
     }
 
     // SetTarget nodes can be handled no matter what their next node is (if they have one)
diff --git a/content/media/webaudio/compiledtest/TestAudioEventTimeline.cpp b/content/media/webaudio/compiledtest/TestAudioEventTimeline.cpp
index 6e0cabe17f9..7ff0bed8361 100644
--- a/content/media/webaudio/compiledtest/TestAudioEventTimeline.cpp
+++ b/content/media/webaudio/compiledtest/TestAudioEventTimeline.cpp
@@ -215,7 +215,7 @@ void TestEventRemoval()
   is(timeline.GetEventCount(), 1u, "Should successfully delete two events");
 }
 
-void TestBeforeFirstEvent()
+void TestBeforeFirstEventSetValue()
 {
   Timeline timeline(10.0f);
 
@@ -225,6 +225,36 @@ void TestBeforeFirstEvent()
   is(timeline.GetValueAtTime(0.5), 10.0f, "Retrun the default value before the first event");
 }
 
+void TestBeforeFirstEventSetTarget()
+{
+  Timeline timeline(10.0f);
+
+  ErrorResultMock rv;
+
+  timeline.SetTargetAtTime(20.0f, 1.0, 5.0, rv);
+  is(timeline.GetValueAtTime(0.5), 10.0f, "Retrun the default value before the first event");
+}
+
+void TestBeforeFirstEventLinearRamp()
+{
+  Timeline timeline(10.0f);
+
+  ErrorResultMock rv;
+
+  timeline.LinearRampToValueAtTime(20.0f, 1.0, rv);
+  is(timeline.GetValueAtTime(0.5), 10.0f, "Retrun the default value before the first event");
+}
+
+void TestBeforeFirstEventExponentialRamp()
+{
+  Timeline timeline(10.0f);
+
+  ErrorResultMock rv;
+
+  timeline.ExponentialRampToValueAtTime(20.0f, 1.0, rv);
+  is(timeline.GetValueAtTime(0.5), 10.0f, "Retrun the default value before the first event");
+}
+
 void TestAfterLastValueEvent()
 {
   Timeline timeline(10.0f);
@@ -361,7 +391,10 @@ int main()
   TestInvalidEvents();
   TestEventReplacement();
   TestEventRemoval();
-  TestBeforeFirstEvent();
+  TestBeforeFirstEventSetValue();
+  TestBeforeFirstEventSetTarget();
+  TestBeforeFirstEventLinearRamp();
+  TestBeforeFirstEventExponentialRamp();
   TestAfterLastValueEvent();
   TestAfterLastTargetValueEvent();
   TestAfterLastTargetValueEventWithValueSet();