diff --git a/services/core/java/com/android/server/am/UserController.java b/services/core/java/com/android/server/am/UserController.java
index a7e95fb93fc5d..aefa2f5bf66e7 100644
--- a/services/core/java/com/android/server/am/UserController.java
+++ b/services/core/java/com/android/server/am/UserController.java
@@ -949,9 +949,8 @@ class UserController implements Handler.Callback {
     int stopUser(final int userId, final boolean force, boolean allowDelayedLocking,
             final IStopUserCallback stopUserCallback, KeyEvictedCallback keyEvictedCallback) {
         checkCallingPermission(INTERACT_ACROSS_USERS_FULL, "stopUser");
-        if (userId < 0 || userId == UserHandle.USER_SYSTEM) {
-            throw new IllegalArgumentException("Can't stop system user " + userId);
-        }
+        Preconditions.checkArgument(userId >= 0, "Invalid user id %d", userId);
+
         enforceShellRestriction(UserManager.DISALLOW_DEBUGGING_FEATURES, userId);
         synchronized (mLock) {
             return stopUsersLU(userId, force, allowDelayedLocking, stopUserCallback,
diff --git a/services/tests/servicestests/src/com/android/server/am/UserControllerTest.java b/services/tests/servicestests/src/com/android/server/am/UserControllerTest.java
index 6e446f04b2fa7..d47f063caec56 100644
--- a/services/tests/servicestests/src/com/android/server/am/UserControllerTest.java
+++ b/services/tests/servicestests/src/com/android/server/am/UserControllerTest.java
@@ -638,6 +638,39 @@ public class UserControllerTest {
                 /* keyEvictedCallback= */ mKeyEvictedCallback, /* expectLocking= */ true);
     }
 
+    @Test
+    public void testStopUser_invalidUser() {
+        int userId = -1;
+
+        assertThrows(IllegalArgumentException.class,
+                () -> mUserController.stopUser(userId, /* force= */ true,
+                        /* allowDelayedLocking= */ true, /* stopUserCallback= */ null,
+                        /* keyEvictedCallback= */ null));
+    }
+
+    @Test
+    public void testStopUser_systemUser() {
+        int userId = UserHandle.USER_SYSTEM;
+
+        int r = mUserController.stopUser(userId, /* force= */ true,
+                /* allowDelayedLocking= */ true, /* stopUserCallback= */ null,
+                /* keyEvictedCallback= */ null);
+
+        assertThat(r).isEqualTo(ActivityManager.USER_OP_ERROR_IS_SYSTEM);
+    }
+
+    @Test
+    public void testStopUser_currentUser() {
+        setUpUser(TEST_USER_ID1, /* flags= */ 0);
+        mUserController.startUser(TEST_USER_ID1, /* foreground= */ true);
+
+        int r = mUserController.stopUser(TEST_USER_ID1, /* force= */ true,
+                /* allowDelayedLocking= */ true, /* stopUserCallback= */ null,
+                /* keyEvictedCallback= */ null);
+
+        assertThat(r).isEqualTo(ActivityManager.USER_OP_IS_CURRENT);
+    }
+
     /**
      * Test conditional delayed locking with mDelayUserDataLocking true.
      */