diff --git a/app/src/main/java/org/thoughtcrime/securesms/registration/fragments/RegistrationLockFragment.java b/app/src/main/java/org/thoughtcrime/securesms/registration/fragments/RegistrationLockFragment.java
index 73fb7a8784..3b79b78429 100644
--- a/app/src/main/java/org/thoughtcrime/securesms/registration/fragments/RegistrationLockFragment.java
+++ b/app/src/main/java/org/thoughtcrime/securesms/registration/fragments/RegistrationLockFragment.java
@@ -3,7 +3,6 @@ package org.thoughtcrime.securesms.registration.fragments;
 import android.content.res.Resources;
 import android.os.Bundle;
 import android.text.InputType;
-import android.text.TextUtils;
 import android.view.LayoutInflater;
 import android.view.View;
 import android.view.ViewGroup;
@@ -35,6 +34,9 @@ public final class RegistrationLockFragment extends BaseRegistrationFragment {
 
   private static final String TAG = Log.tag(RegistrationLockFragment.class);
 
+  /** Applies to both V1 and V2 pins, because some V2 pins may have been migrated from V1. */
+  private static final int MINIMUM_PIN_LENGTH = 4;
+
   private EditText               pinEntry;
   private View                   forgotPin;
   private CircularProgressButton pinButton;
@@ -129,11 +131,17 @@ public final class RegistrationLockFragment extends BaseRegistrationFragment {
   private void handlePinEntry() {
     final String pin = pinEntry.getText().toString();
 
-    if (TextUtils.isEmpty(pin) || TextUtils.isEmpty(pin.replace(" ", ""))) {
+    int trimmedLength = pin.replace(" ", "").length();
+    if (trimmedLength == 0) {
       Toast.makeText(requireContext(), R.string.RegistrationActivity_you_must_enter_your_registration_lock_PIN, Toast.LENGTH_LONG).show();
       return;
     }
 
+    if (trimmedLength < MINIMUM_PIN_LENGTH) {
+      Toast.makeText(requireContext(), getString(R.string.RegistrationActivity_your_pin_has_at_least_d_digits_or_characters, MINIMUM_PIN_LENGTH), Toast.LENGTH_LONG).show();
+      return;
+    }
+
     RegistrationViewModel model                   = getModel();
     RegistrationService   registrationService     = RegistrationService.getInstance(model.getNumber().getE164Number(), model.getRegistrationSecret());
     TokenResponse         tokenResponse           = model.getKeyBackupCurrentToken();
diff --git a/app/src/main/res/values/strings.xml b/app/src/main/res/values/strings.xml
index 6f270e44a0..e74e0b6606 100644
--- a/app/src/main/res/values/strings.xml
+++ b/app/src/main/res/values/strings.xml
@@ -1866,6 +1866,7 @@
     <string name="preferences_app_protection__registration_lock_pin">Registration Lock PIN</string>
     <string name="preferences_app_protection__registration_lock">Registration Lock</string>
     <string name="RegistrationActivity_you_must_enter_your_registration_lock_PIN">You must enter your Registration Lock PIN</string>
+    <string name="RegistrationActivity_your_pin_has_at_least_d_digits_or_characters">Your pin has at least %d digits or characters</string>
     <string name="RegistrationActivity_incorrect_registration_lock_pin">Incorrect Registration Lock PIN</string>
     <string name="RegistrationActivity_too_many_attempts">Too many attempts</string>
     <string name="RegistrationActivity_you_have_made_too_many_incorrect_registration_lock_pin_attempts_please_try_again_in_a_day">You\'ve made too many incorrect Registration Lock PIN attempts. Please try again in a day.</string>