diff --git a/app/build.gradle b/app/build.gradle
index e88f74c6..586e988c 100644
--- a/app/build.gradle
+++ b/app/build.gradle
@@ -6,6 +6,7 @@ apply plugin: 'io.fabric'
 apply plugin: 'com.github.triplet.play'
 apply from: 'jacoco.gradle'
 apply from: 'sonarqube.gradle'
+apply from: 'hooks.gradle'
 
 android {
     compileSdkVersion 28
@@ -16,8 +17,8 @@ android {
         testApplicationId "io.github.tests.wulkanowy"
         minSdkVersion 15
         targetSdkVersion 28
-        versionCode 38
-        versionName "0.9.0"
+        versionCode 39
+        versionName "0.9.1"
         multiDexEnabled true
         testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
         vectorDrawables.useSupportLibrary = true
@@ -97,7 +98,7 @@ play {
 }
 
 dependencies {
-    implementation 'io.github.wulkanowy:api:0.9.0'
+    implementation 'io.github.wulkanowy:api:0.9.1'
 
     implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk8:$kotlin_version"
     implementation "androidx.legacy:legacy-support-v4:1.0.0"
@@ -106,7 +107,7 @@ dependencies {
 
     implementation "androidx.cardview:cardview:1.0.0"
     implementation 'androidx.constraintlayout:constraintlayout:1.1.3'
-    implementation "com.google.android.material:material:1.1.0-alpha07"
+    implementation "com.google.android.material:material:1.1.0-alpha05"
     implementation 'com.github.wulkanowy:MaterialChipsInput:b72fd0ee6f'
     implementation 'com.github.PhilJay:MPAndroidChart:v3.1.0'
 
diff --git a/app/hooks.gradle b/app/hooks.gradle
new file mode 100644
index 00000000..038fa9fb
--- /dev/null
+++ b/app/hooks.gradle
@@ -0,0 +1,10 @@
+apply plugin: "com.star-zero.gradle.githook"
+
+githook {
+    failOnMissingHooksDir = false
+    hooks {
+        "pre-push" {
+            shell = "./app/play-publish-lint.sh"
+        }
+    }
+}
diff --git a/app/play-publish-lint.sh b/app/play-publish-lint.sh
new file mode 100755
index 00000000..d3354b1a
--- /dev/null
+++ b/app/play-publish-lint.sh
@@ -0,0 +1,7 @@
+#!/bin/bash -
+
+content=$(cat < "app/src/main/play/release-notes/pl-PL/default.txt") || exit
+if [[ "${#content}" -gt 500 ]]; then
+    echo >&2 "Release notes content has reached the limit of 500 characters"
+    exit 1
+fi
diff --git a/app/src/main/java/io/github/wulkanowy/data/repositories/preferences/PreferencesRepository.kt b/app/src/main/java/io/github/wulkanowy/data/repositories/preferences/PreferencesRepository.kt
index bde84162..bb9a39b1 100644
--- a/app/src/main/java/io/github/wulkanowy/data/repositories/preferences/PreferencesRepository.kt
+++ b/app/src/main/java/io/github/wulkanowy/data/repositories/preferences/PreferencesRepository.kt
@@ -20,6 +20,9 @@ class PreferencesRepository @Inject constructor(
     val gradeAverageMode: String
         get() = sharedPref.getString(context.getString(R.string.pref_key_grade_average_mode), "only_one_semester") ?: "only_one_semester"
 
+    val gradeAverageForceCalc: Boolean
+        get() = sharedPref.getBoolean(context.getString(R.string.pref_key_grade_average_force_calc), false)
+
     val isGradeExpandable: Boolean
         get() = !sharedPref.getBoolean(context.getString(R.string.pref_key_expand_grade), false)
 
diff --git a/app/src/main/java/io/github/wulkanowy/ui/modules/grade/GradeAverageProvider.kt b/app/src/main/java/io/github/wulkanowy/ui/modules/grade/GradeAverageProvider.kt
index cff60268..3f794ff1 100644
--- a/app/src/main/java/io/github/wulkanowy/ui/modules/grade/GradeAverageProvider.kt
+++ b/app/src/main/java/io/github/wulkanowy/ui/modules/grade/GradeAverageProvider.kt
@@ -67,6 +67,6 @@ class GradeAverageProvider @Inject constructor(
                 if (it.any { summary -> summary.average != .0 }) {
                     Maybe.just(it.map { summary -> summary.subject to summary.average }.toMap())
                 } else Maybe.empty()
-            }
+            }.filter { !preferencesRepository.gradeAverageForceCalc }
     }
 }
diff --git a/app/src/main/play/release-notes/pl-PL/default.txt b/app/src/main/play/release-notes/pl-PL/default.txt
index 7fe143d8..e2048e1f 100644
--- a/app/src/main/play/release-notes/pl-PL/default.txt
+++ b/app/src/main/play/release-notes/pl-PL/default.txt
@@ -2,7 +2,7 @@ Wersja 0.9.0
 
 Dodaliśmy:
 - zarządzanie dostępem mobilnym do dziennika
-- wyświetlanie sumy punktów (jeśli dziennik obsługuje)
+- wyświetlanie sumy punktów
 - wyświetlanie informacji o wygasłej sesji, gdy zostanie zmienione hasło
 
 Naprawiliśmy:
diff --git a/app/src/main/res/values-pl/strings.xml b/app/src/main/res/values-pl/strings.xml
index 128d8636..91d980a6 100644
--- a/app/src/main/res/values-pl/strings.xml
+++ b/app/src/main/res/values-pl/strings.xml
@@ -253,6 +253,7 @@
     <string name="pref_view_header">Wygląd</string>
     <string name="pref_view_list">Domyślny widok</string>
     <string name="pref_view_grade_average_mode">Obliczanie średniej końcoworocznej</string>
+    <string name="pref_view_grade_average_force_calc">Wymuś obliczanie średniej przez aplikację</string>
     <string name="pref_view_present">Pokazuj obecność we frekwencji</string>
     <string name="pref_view_app_theme">Motyw aplikacji</string>
     <string name="pref_view_expand_grade">Rozwiń oceny</string>
diff --git a/app/src/main/res/values/preferences_keys.xml b/app/src/main/res/values/preferences_keys.xml
index b09ee51b..730fea59 100644
--- a/app/src/main/res/values/preferences_keys.xml
+++ b/app/src/main/res/values/preferences_keys.xml
@@ -6,6 +6,7 @@
     <string name="pref_key_grade_color_scheme">grade_color_scheme</string>
     <string name="pref_key_expand_grade">expand_grade</string>
     <string name="pref_key_grade_average_mode">grade_average_mode</string>
+    <string name="pref_key_grade_average_force_calc">grade_average_always_calc</string>
     <string name="pref_key_services_enable">services_enable</string>
     <string name="pref_key_services_interval">services_interval</string>
     <string name="pref_key_services_wifi_only">services_disable_wifi_only</string>
diff --git a/app/src/main/res/values/strings.xml b/app/src/main/res/values/strings.xml
index b6424876..fd94e5b6 100644
--- a/app/src/main/res/values/strings.xml
+++ b/app/src/main/res/values/strings.xml
@@ -237,6 +237,7 @@
     <string name="pref_view_header">Appearance</string>
     <string name="pref_view_list">Default view</string>
     <string name="pref_view_grade_average_mode">Calculation of the end-of-year average</string>
+    <string name="pref_view_grade_average_force_calc">Force average calculation by app</string>
     <string name="pref_view_present">Show presence in attendance</string>
     <string name="pref_view_app_theme">Application theme</string>
     <string name="pref_view_expand_grade">Expand grades</string>
diff --git a/app/src/main/res/xml/scheme_preferences.xml b/app/src/main/res/xml/scheme_preferences.xml
index 149024c0..ccacfe9d 100644
--- a/app/src/main/res/xml/scheme_preferences.xml
+++ b/app/src/main/res/xml/scheme_preferences.xml
@@ -105,6 +105,11 @@
             android:summary="%s"
             android:title="@string/pref_view_grade_average_mode"
             app:iconSpaceReserved="false" />
+        <SwitchPreference
+            android:defaultValue="false"
+            android:key="@string/pref_key_grade_average_force_calc"
+            android:title="@string/pref_view_grade_average_force_calc"
+            app:iconSpaceReserved="false" />
         <SwitchPreference
             android:defaultValue="true"
             android:key="@string/pref_key_fill_message_content"
diff --git a/app/src/test/java/io/github/wulkanowy/ui/modules/grade/GradeAverageProviderTest.kt b/app/src/test/java/io/github/wulkanowy/ui/modules/grade/GradeAverageProviderTest.kt
index e1ac99d6..3197bb79 100644
--- a/app/src/test/java/io/github/wulkanowy/ui/modules/grade/GradeAverageProviderTest.kt
+++ b/app/src/test/java/io/github/wulkanowy/ui/modules/grade/GradeAverageProviderTest.kt
@@ -59,6 +59,7 @@ class GradeAverageProviderTest {
 
         doReturn(.33).`when`(preferencesRepository).gradeMinusModifier
         doReturn(.33).`when`(preferencesRepository).gradePlusModifier
+        doReturn(false).`when`(preferencesRepository).gradeAverageForceCalc
 
         doReturn(Single.just(firstGrades)).`when`(gradeRepository).getGrades(student, semesters[1], true)
         doReturn(Single.just(secondGrade)).`when`(gradeRepository).getGrades(student, semesters[2], true)
@@ -128,6 +129,24 @@ class GradeAverageProviderTest {
         assertEquals(3.26, averages["Fizyka"])
     }
 
+    @Test
+    fun onlyOneSemester_averageFromSummary_forceCalc() {
+        doReturn(true).`when`(preferencesRepository).gradeAverageForceCalc
+        doReturn("all_year").`when`(preferencesRepository).gradeAverageMode
+        doReturn(Single.just(firstGrades)).`when`(gradeRepository).getGrades(student, semesters[1], false)
+        doReturn(Single.just(listOf(
+            getSummary(22, "Matematyka", 3.1),
+            getSummary(22, "Fizyka", 3.26)
+        ))).`when`(gradeSummaryRepository).getGradesSummary(semesters[2], true)
+
+        val averages = gradeAverageProvider.getGradeAverage(student, semesters, semesters[2].semesterId, true)
+            .blockingGet()
+
+        assertEquals(2, averages.size)
+        assertEquals(3.0, averages["Matematyka"])
+        assertEquals(3.25, averages["Fizyka"])
+    }
+
     private fun getGrade(semesterId: Int, subject: String, value: Int): Grade {
         return Grade(
             studentId = 101,
diff --git a/build.gradle b/build.gradle
index 4ed9ec68..ac8a0926 100644
--- a/build.gradle
+++ b/build.gradle
@@ -14,6 +14,7 @@ buildscript {
         classpath "io.fabric.tools:gradle:1.29.0"
         classpath "com.github.triplet.gradle:play-publisher:2.2.1"
         classpath "org.sonarsource.scanner.gradle:sonarqube-gradle-plugin:2.7.1"
+        classpath "gradle.plugin.com.star-zero.gradle:githook:1.1.0"
     }
 }