diff --git a/src/com/android/server/telecom/InCallController.java b/src/com/android/server/telecom/InCallController.java
index 06d8fdc..766cb12 100644
--- a/src/com/android/server/telecom/InCallController.java
+++ b/src/com/android/server/telecom/InCallController.java
@@ -947,6 +947,15 @@
         }
     };
 
+    private final BroadcastReceiver mUserAddedReceiver = new BroadcastReceiver() {
+        @Override
+        public void onReceive(Context context, Intent intent) {
+            if (Intent.ACTION_USER_ADDED.equals(intent.getAction())) {
+                restrictPhoneCallOps();
+            }
+        }
+    };
+
     private final SystemStateListener mSystemStateListener = new SystemStateListener() {
         @Override
         public void onCarModeChanged(int priority, String packageName, boolean isCarMode) {
@@ -1055,6 +1064,7 @@
         mSystemStateHelper.addListener(mSystemStateListener);
         mClockProxy = clockProxy;
         restrictPhoneCallOps();
+        mContext.registerReceiver(mUserAddedReceiver, new IntentFilter(Intent.ACTION_USER_ADDED));
     }
 
     private void restrictPhoneCallOps() {
diff --git a/src/com/android/server/telecom/PhoneAccountRegistrar.java b/src/com/android/server/telecom/PhoneAccountRegistrar.java
index bce6e43..d8f2d22 100644
--- a/src/com/android/server/telecom/PhoneAccountRegistrar.java
+++ b/src/com/android/server/telecom/PhoneAccountRegistrar.java
@@ -134,6 +134,7 @@
     public static final String FILE_NAME = "phone-account-registrar-state.xml";
     @VisibleForTesting
     public static final int EXPECTED_STATE_VERSION = 9;
+    public static final int MAX_PHONE_ACCOUNT_REGISTRATIONS = 10;
 
     /** Keep in sync with the same in SipSettings.java */
     private static final String SIP_SHARED_PREFERENCES = "SIP_PREFERENCES";
@@ -766,8 +767,13 @@
         return account.isSelfManaged();
     }
 
-    // TODO: Should we implement an artificial limit for # of accounts associated with a single
-    // ComponentName?
+    /**
+     * Performs checks before calling addOrReplacePhoneAccount(PhoneAccount)
+     *
+     * @param account The {@code PhoneAccount} to add or replace.
+     * @throws SecurityException if package does not have BIND_TELECOM_CONNECTION_SERVICE permission
+     * @throws IllegalArgumentException if MAX_PHONE_ACCOUNT_REGISTRATIONS are reached
+     */
     public void registerPhoneAccount(PhoneAccount account) {
         // Enforce the requirement that a connection service for a phone account has the correct
         // permission.
@@ -778,6 +784,19 @@
             throw new SecurityException("PhoneAccount connection service requires "
                     + "BIND_TELECOM_CONNECTION_SERVICE permission.");
         }
+        //Enforce an upper bound on the number of PhoneAccount's a package can register.
+        // Most apps should only require 1-2.
+        if (getPhoneAccountsForPackage(
+                account.getAccountHandle().getComponentName().getPackageName(),
+                account.getAccountHandle().getUserHandle()).size()
+                >= MAX_PHONE_ACCOUNT_REGISTRATIONS) {
+            Log.w(this, "Phone account %s reached max registration limit for package",
+                    account.getAccountHandle());
+            throw new IllegalArgumentException(
+                    "Error, cannot register phone account " + account.getAccountHandle()
+                            + " because the limit, " + MAX_PHONE_ACCOUNT_REGISTRATIONS
+                            + ", has been reached");
+        }
 
         addOrReplacePhoneAccount(account);
     }