diff --git a/app/src/main/java/info/nightscout/androidaps/MainActivity.java b/app/src/main/java/info/nightscout/androidaps/MainActivity.java
index b702897ba4..e77be36ba6 100644
--- a/app/src/main/java/info/nightscout/androidaps/MainActivity.java
+++ b/app/src/main/java/info/nightscout/androidaps/MainActivity.java
@@ -82,7 +82,7 @@ public class MainActivity extends AppCompatActivity implements View.OnClickListe
                     Manifest.permission.WRITE_EXTERNAL_STORAGE}, CASE_STORAGE);
         }
         askForBatteryOptimizationPermission();
-        checkUpgradeToProfileTarget();
+        doMigrations();
         if (Config.logFunctionCalls)
             log.debug("onCreate");
 
@@ -163,6 +163,19 @@ public class MainActivity extends AppCompatActivity implements View.OnClickListe
         }
     }
 
+    private void doMigrations() {
+
+        checkUpgradeToProfileTarget();
+
+        // guarantee that the unreachable threshold is at least 30 and of type String
+        // Added in 1.57 at 21.01.2018
+        Integer unreachable_threshold = SP.getInt(R.string.key_pump_unreachable_threshold, 30);
+        SP.remove(R.string.key_pump_unreachable_threshold);
+        if(unreachable_threshold < 30) unreachable_threshold = 30;
+        SP.putString(R.string.key_pump_unreachable_threshold, unreachable_threshold.toString());
+    }
+
+
     private void checkUpgradeToProfileTarget() { // TODO: can be removed in the future
         boolean oldKeyExists = SP.contains("openapsma_min_bg");
         if (oldKeyExists) {
diff --git a/app/src/main/res/xml/pref_others.xml b/app/src/main/res/xml/pref_others.xml
index 548b99e5b9..ba16f09c2f 100644
--- a/app/src/main/res/xml/pref_others.xml
+++ b/app/src/main/res/xml/pref_others.xml
@@ -1,5 +1,6 @@
 <?xml version="1.0" encoding="utf-8"?>
-<PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android">
+<PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:validate="http://schemas.android.com/apk/res-auto">
     <PreferenceCategory
         android:key="others"
         android:title="@string/othersettings_title">
@@ -76,12 +77,16 @@
             android:defaultValue="true"
             android:key="@string/key_enable_pump_unreachable_alert"
             android:title="@string/enable_pump_unreachable_alert" />
-        <EditTextPreference
+        <com.andreabaccega.widget.ValidatingEditTextPreference
+            validate:testType="numericRange"
+            validate:minNumber="30"
+            validate:maxNumber="300"
             android:defaultValue="30"
             android:dependency="@string/key_enable_pump_unreachable_alert"
             android:inputType="number"
             android:key="@string/key_pump_unreachable_threshold"
-            android:title="@string/pump_unreachable_threshold"></EditTextPreference>
+            android:title="@string/pump_unreachable_threshold">
+        </com.andreabaccega.widget.ValidatingEditTextPreference>
     </PreferenceScreen>
     <SwitchPreference
         android:defaultValue="false"