diff --git a/core/java/android/service/autofill/AutofillServiceHelper.java b/core/java/android/service/autofill/AutofillServiceHelper.java
new file mode 100644
index 0000000000000..bbaebff439fb5
--- /dev/null
+++ b/core/java/android/service/autofill/AutofillServiceHelper.java
@@ -0,0 +1,35 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package android.service.autofill;
+
+import android.annotation.Nullable;
+import android.view.autofill.AutofillId;
+
+import com.android.internal.util.Preconditions;
+
+/** @hide */
+final class AutofillServiceHelper {
+
+    static AutofillId[] assertValid(@Nullable AutofillId[] ids) {
+        Preconditions.checkArgument(ids != null && ids.length > 0, "must have at least one id");
+        return Preconditions.checkArrayElementsNotNull(ids, "ids");
+    }
+
+    private AutofillServiceHelper() {
+        throw new UnsupportedOperationException("contains static members only");
+    }
+}
diff --git a/core/java/android/service/autofill/FillResponse.java b/core/java/android/service/autofill/FillResponse.java
index 3a4b6bb8037ed..be84ba9d837d2 100644
--- a/core/java/android/service/autofill/FillResponse.java
+++ b/core/java/android/service/autofill/FillResponse.java
@@ -16,6 +16,7 @@
 
 package android.service.autofill;
 
+import static android.service.autofill.AutofillServiceHelper.assertValid;
 import static android.service.autofill.FillRequest.INVALID_REQUEST_ID;
 import static android.view.autofill.Helper.sDebug;
 
@@ -245,10 +246,15 @@ public final class FillResponse implements Parcelable {
          * @param ids id of Views that when focused will display the authentication UI.
          *
          * @return This builder.
-
-         * @throws IllegalArgumentException if {@code ids} is {@code null} or empty, or if
-         * both {@code authentication} and {@code presentation} are {@code null}, or if
-         * both {@code authentication} and {@code presentation} are non-{@code null}
+         *
+         * @throws IllegalArgumentException if any of the following occurs:
+         * <ul>
+         *   <li>{@code ids} is {@code null}</li>
+         *   <li>{@code ids} is empty</li>
+         *   <li>{@code ids} contains a {@code null} element</li>
+         *   <li>both {@code authentication} and {@code presentation} are {@code null}</li>
+         *   <li>both {@code authentication} and {@code presentation} are non-{@code null}</li>
+         * </ul>
          *
          * @throws IllegalStateException if a {@link #setHeader(RemoteViews) header} or a
          * {@link #setFooter(RemoteViews) footer} are already set for this builder.
@@ -263,16 +269,13 @@ public final class FillResponse implements Parcelable {
                 throw new IllegalStateException("Already called #setHeader() or #setFooter()");
             }
 
-            if (ids == null || ids.length == 0) {
-                throw new IllegalArgumentException("ids cannot be null or empry");
-            }
             if (authentication == null ^ presentation == null) {
                 throw new IllegalArgumentException("authentication and presentation"
                         + " must be both non-null or null");
             }
             mAuthentication = authentication;
             mPresentation = presentation;
-            mAuthenticationIds = ids;
+            mAuthenticationIds = assertValid(ids);
             return this;
         }
 
diff --git a/core/java/android/service/autofill/SaveInfo.java b/core/java/android/service/autofill/SaveInfo.java
index a5a6177dedc39..1be1be64548a9 100644
--- a/core/java/android/service/autofill/SaveInfo.java
+++ b/core/java/android/service/autofill/SaveInfo.java
@@ -16,6 +16,7 @@
 
 package android.service.autofill;
 
+import static android.service.autofill.AutofillServiceHelper.assertValid;
 import static android.view.autofill.Helper.sDebug;
 
 import android.annotation.IntDef;
@@ -405,17 +406,6 @@ public final class SaveInfo implements Parcelable {
             mRequiredIds = null;
         }
 
-        private AutofillId[] assertValid(AutofillId[] ids) {
-            Preconditions.checkArgument(ids != null && ids.length > 0,
-                    "must have at least one id: " + Arrays.toString(ids));
-            for (int i = 0; i < ids.length; i++) {
-                final AutofillId id = ids[i];
-                Preconditions.checkArgument(id != null,
-                        "cannot have null id: " + Arrays.toString(ids));
-            }
-            return ids;
-        }
-
         /**
          * Sets flags changing the save behavior.
          *