diff --git a/layout/style/nsAnimationManager.cpp b/layout/style/nsAnimationManager.cpp
index 9063cad57bce..0afa78885d97 100644
--- a/layout/style/nsAnimationManager.cpp
+++ b/layout/style/nsAnimationManager.cpp
@@ -233,9 +233,6 @@ ElementAnimations::GetEventsAt(TimeStamp aRefreshTime,
     ComputedTiming computedTiming =
       ElementAnimation::GetComputedTimingAt(elapsedDuration, anim->mTiming);
 
-    // FIXME: Bug 1004361: If our active duration is sufficiently short and our
-    // samples are sufficiently infrequent we will end up skipping the start
-    // event and jumping straight to the end event.
     switch (computedTiming.mPhase) {
       case ComputedTiming::AnimationPhase_Before:
         // Do nothing
@@ -262,6 +259,18 @@ ElementAnimations::GetEventsAt(TimeStamp aRefreshTime,
         break;
 
       case ComputedTiming::AnimationPhase_After:
+        // If we skipped the animation interval entirely, dispatch
+        // 'animationstart' first
+        if (anim->mLastNotification ==
+            ElementAnimation::LAST_NOTIFICATION_NONE) {
+          // Notifying for start of 0th iteration.
+          // (This is overwritten below but we set it here to maintain
+          // internal consistency.)
+          anim->mLastNotification = 0;
+          AnimationEventInfo ei(mElement, anim->mName, NS_ANIMATION_START,
+                                elapsedDuration, PseudoElement());
+          aEventsToDispatch.AppendElement(ei);
+        }
         // Dispatch 'animationend' when needed.
         if (anim->mLastNotification !=
             ElementAnimation::LAST_NOTIFICATION_END) {
diff --git a/layout/style/test/test_animations.html b/layout/style/test/test_animations.html
index 8c98d47142ae..9c44d2338210 100644
--- a/layout/style/test/test_animations.html
+++ b/layout/style/test/test_animations.html
@@ -1539,6 +1539,25 @@ dyn_sheet_elt.parentNode.removeChild(dyn_sheet_elt);
 dyn_sheet_elt = null;
 dyn_sheet = null;
 
+/*
+ * Bug 1004361 - CSS animations with short duration sometimes don't dispatch
+ * a start event
+ */
+new_div("animation: anim2 1s 0.1s");
+listen();
+advance_clock(0); // Trigger animation
+advance_clock(1200); // Skip past end of animation's entire active duration
+check_events([{ type: 'animationstart', target: div,
+                // Bug 1007513 - elapsedTime should be 0 below
+                animationName: 'anim2', elapsedTime: 1.1,
+                pseudoElement: "" },
+              { type: 'animationend', target: div,
+                // Bug 1007513 - elapsedTime should be 1 below
+                animationName: 'anim2', elapsedTime: 1.1,
+                pseudoElement: "" }],
+             "events after skipping over animation interval");
+done_div();
+
 SpecialPowers.DOMWindowUtils.restoreNormalRefresh();
 
 </script>
diff --git a/layout/style/test/test_animations_omta.html b/layout/style/test/test_animations_omta.html
index 398405fab32d..e4facc193c09 100644
--- a/layout/style/test/test_animations_omta.html
+++ b/layout/style/test/test_animations_omta.html
@@ -1845,6 +1845,28 @@ addAsyncTest(function *() {
   dyn_sheet = null;
 });
 
+/*
+ * Bug 1004361 - CSS animations with short duration sometimes don't dispatch
+ * a start event
+ */
+addAsyncTest(function *() {
+  new_div("animation: anim2 1s 0.1s");
+  listen();
+  yield waitForPaints();
+  advance_clock(0); // Trigger animation
+  advance_clock(1200); // Skip past end of animation's entire active duration
+  check_events([{ type: 'animationstart', target: gDiv,
+                  // Bug 1007513 - elapsedTime should be 0 below
+                  animationName: 'anim2', elapsedTime: 1.1,
+                  pseudoElement: "" },
+                { type: 'animationend', target: gDiv,
+                  // Bug 1007513 - elapsedTime should be 1 below
+                  animationName: 'anim2', elapsedTime: 1.1,
+                  pseudoElement: "" }],
+               "events after skipping over animation interval");
+  done_div();
+});
+
 //----------------------------------------------------------------------
 //
 // Helper functions from test_animations.html