diff --git a/core/res/res/values/attrs_manifest.xml b/core/res/res/values/attrs_manifest.xml
index c51b2d84ab6d2..588ae79cda1df 100644
--- a/core/res/res/values/attrs_manifest.xml
+++ b/core/res/res/values/attrs_manifest.xml
@@ -826,7 +826,7 @@
             that created the task, and therefore there will only be one instance of this activity
             in a task. In constrast to the {@code singleTask} launch mode, this activity can be
             started in multiple instances in different tasks if the
-            {@code FLAG_ACTIVITY_MULTIPLE_TASK} is set.-->
+            {@code FLAG_ACTIVITY_MULTIPLE_TASK} or {@code FLAG_ACTIVITY_NEW_DOCUMENT} is set.-->
         <enum name="singleInstancePerTask" value="4" />
     </attr>
     <!-- Specify the orientation an activity should be run in.  If not
diff --git a/services/core/java/com/android/server/wm/ActivityStarter.java b/services/core/java/com/android/server/wm/ActivityStarter.java
index 75a188ed86a25..1158a9c70158e 100644
--- a/services/core/java/com/android/server/wm/ActivityStarter.java
+++ b/services/core/java/com/android/server/wm/ActivityStarter.java
@@ -2721,8 +2721,22 @@ class ActivityStarter {
                     launchFlags |= Intent.FLAG_ACTIVITY_NEW_DOCUMENT;
                     break;
                 case ActivityInfo.DOCUMENT_LAUNCH_NEVER:
-                    launchFlags &=
-                            ~(Intent.FLAG_ACTIVITY_NEW_DOCUMENT | FLAG_ACTIVITY_MULTIPLE_TASK);
+                    if (mLaunchMode == LAUNCH_SINGLE_INSTANCE_PER_TASK) {
+                        // Remove MULTIPLE_TASK flag along with NEW_DOCUMENT only if NEW_DOCUMENT
+                        // is set, otherwise we still want to keep the MULTIPLE_TASK flag (if
+                        // any) for singleInstancePerTask that the multiple tasks can be created,
+                        // or a singleInstancePerTask activity is basically the same as a
+                        // singleTask activity when documentLaunchMode set to never.
+                        if ((launchFlags & Intent.FLAG_ACTIVITY_NEW_DOCUMENT) != 0) {
+                            launchFlags &= ~(Intent.FLAG_ACTIVITY_NEW_DOCUMENT
+                                    | FLAG_ACTIVITY_MULTIPLE_TASK);
+                        }
+                    } else {
+                        // TODO(b/184903976): Should FLAG_ACTIVITY_MULTIPLE_TASK always be
+                        // removed for document-never activity?
+                        launchFlags &=
+                                ~(Intent.FLAG_ACTIVITY_NEW_DOCUMENT | FLAG_ACTIVITY_MULTIPLE_TASK);
+                    }
                     break;
             }
         }