diff --git a/libs/WindowManager/Shell/src/com/android/wm/shell/transition/Transitions.java b/libs/WindowManager/Shell/src/com/android/wm/shell/transition/Transitions.java
index 8e7b9df..155990a 100644
--- a/libs/WindowManager/Shell/src/com/android/wm/shell/transition/Transitions.java
+++ b/libs/WindowManager/Shell/src/com/android/wm/shell/transition/Transitions.java
@@ -799,6 +799,12 @@
                 ++mergeIdx;
                 continue;
             }
+            if (mergeCandidate.mInfo == null) {
+                ProtoLog.v(ShellProtoLogGroup.WM_SHELL_TRANSITIONS, "Transition merge candidate"
+                        + " %s is not ready yet", mergeCandidate.mToken);
+                // The later transition should not be merged if the prior one is not ready.
+                return;
+            }
             if (mergeCandidate.mMerged) {
                 throw new IllegalStateException("Can't merge a transition after not-merging"
                         + " a preceding one.");
diff --git a/libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/transition/ShellTransitionTests.java b/libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/transition/ShellTransitionTests.java
index 6c9b186..e63bbeb 100644
--- a/libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/transition/ShellTransitionTests.java
+++ b/libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/transition/ShellTransitionTests.java
@@ -563,6 +563,33 @@
         assertEquals(0, mDefaultHandler.activeCount());
     }
 
+
+    @Test
+    public void testTransitionMergingOnFinish() {
+        final Transitions transitions = createTestTransitions();
+        transitions.replaceDefaultHandlerForTest(mDefaultHandler);
+
+        // The current transition.
+        final IBinder transitToken1 = new Binder();
+        requestStartTransition(transitions, transitToken1);
+        onTransitionReady(transitions, transitToken1);
+
+        // The next ready transition.
+        final IBinder transitToken2 = new Binder();
+        requestStartTransition(transitions, transitToken2);
+        onTransitionReady(transitions, transitToken2);
+
+        // The non-ready merge candidate.
+        final IBinder transitTokenNotReady = new Binder();
+        requestStartTransition(transitions, transitTokenNotReady);
+
+        mDefaultHandler.setSimulateMerge(true);
+        mDefaultHandler.mFinishes.get(0).onTransitionFinished(null /* wct */, null /* wctCB */);
+
+        // Make sure that the non-ready transition is not merged.
+        assertEquals(0, mDefaultHandler.mergeCount());
+    }
+
     @Test
     public void testTransitionOrderMatchesCore() {
         Transitions transitions = createTestTransitions();
@@ -1036,6 +1063,21 @@
         }
     }
 
+    private static void requestStartTransition(Transitions transitions, IBinder token) {
+        transitions.requestStartTransition(token,
+                new TransitionRequestInfo(TRANSIT_OPEN, null /* trigger */, null /* remote */));
+    }
+
+    private static void onTransitionReady(Transitions transitions, IBinder token) {
+        transitions.onTransitionReady(token, createTransitionInfo(),
+                mock(SurfaceControl.Transaction.class), mock(SurfaceControl.Transaction.class));
+    }
+
+    private static TransitionInfo createTransitionInfo() {
+        return new TransitionInfoBuilder(TRANSIT_OPEN)
+                .addChange(TRANSIT_OPEN).addChange(TRANSIT_CLOSE).build();
+    }
+
     private static SurfaceControl createMockSurface(boolean valid) {
         SurfaceControl sc = mock(SurfaceControl.class);
         doReturn(valid).when(sc).isValid();