diff --git a/.travis.yml b/.travis.yml
index c2361d66..a36c34cf 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -14,7 +14,7 @@ cache:
 branches:
   only:
     - develop
-    - 0.21.0
+    - 0.21.1
 
 android:
  licenses:
diff --git a/app/build.gradle b/app/build.gradle
index 0dd31527..cee711d2 100644
--- a/app/build.gradle
+++ b/app/build.gradle
@@ -18,8 +18,8 @@ android {
         testApplicationId "io.github.tests.wulkanowy"
         minSdkVersion 17
         targetSdkVersion 29
-        versionCode 70
-        versionName "0.21.0"
+        versionCode 71
+        versionName "0.21.1"
         multiDexEnabled true
         resValue "string", "app_name", "Wulkanowy"
         testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
@@ -127,7 +127,7 @@ configurations.all {
 }
 
 dependencies {
-    implementation "io.github.wulkanowy:sdk:0.21.0"
+    implementation "io.github.wulkanowy:sdk:0.21.1"
 
     coreLibraryDesugaring 'com.android.tools:desugar_jdk_libs:1.0.10'
 
diff --git a/app/src/main/java/io/github/wulkanowy/data/db/Converters.kt b/app/src/main/java/io/github/wulkanowy/data/db/Converters.kt
index 834a9636..def0b371 100644
--- a/app/src/main/java/io/github/wulkanowy/data/db/Converters.kt
+++ b/app/src/main/java/io/github/wulkanowy/data/db/Converters.kt
@@ -3,6 +3,7 @@ package io.github.wulkanowy.data.db
 import androidx.room.TypeConverter
 import com.squareup.moshi.Moshi
 import com.squareup.moshi.Types
+import io.github.wulkanowy.data.db.adapters.PairAdapterFactory
 import java.time.Instant
 import java.time.LocalDate
 import java.time.LocalDateTime
@@ -12,14 +13,14 @@ import java.util.Date
 
 class Converters {
 
-    private val moshi by lazy { Moshi.Builder().build() }
+    private val moshi by lazy { Moshi.Builder().add(PairAdapterFactory).build() }
 
     private val integerListAdapter by lazy {
         moshi.adapter<List<Int>>(Types.newParameterizedType(List::class.java, Integer::class.java))
     }
 
-    private val stringMapAdapter by lazy {
-        moshi.adapter<Map<String, String>>(Types.newParameterizedType(MutableMap::class.java, String::class.java, String::class.java))
+    private val stringListPairAdapter by lazy {
+        moshi.adapter<List<Pair<String, String>>>(Types.newParameterizedType(List::class.java, Pair::class.java, String::class.java, String::class.java))
     }
 
     @TypeConverter
@@ -60,11 +61,11 @@ class Converters {
 
     @TypeConverter
     fun stringPairListToJson(list: List<Pair<String, String>>): String {
-        return stringMapAdapter.toJson(list.toMap())
+        return stringListPairAdapter.toJson(list)
     }
 
     @TypeConverter
     fun jsonToStringPairList(value: String): List<Pair<String, String>> {
-        return stringMapAdapter.fromJson(value).orEmpty().toList()
+        return stringListPairAdapter.fromJson(value).orEmpty()
     }
 }
diff --git a/app/src/main/java/io/github/wulkanowy/data/db/adapters/PairAdapterFactory.kt b/app/src/main/java/io/github/wulkanowy/data/db/adapters/PairAdapterFactory.kt
new file mode 100644
index 00000000..60ae37c9
--- /dev/null
+++ b/app/src/main/java/io/github/wulkanowy/data/db/adapters/PairAdapterFactory.kt
@@ -0,0 +1,68 @@
+package io.github.wulkanowy.data.db.adapters
+
+import com.squareup.moshi.JsonAdapter
+import com.squareup.moshi.JsonReader
+import com.squareup.moshi.JsonWriter
+import com.squareup.moshi.Moshi
+import com.squareup.moshi.Types
+import java.lang.reflect.ParameterizedType
+import java.lang.reflect.Type
+
+object PairAdapterFactory : JsonAdapter.Factory {
+
+    override fun create(type: Type, annotations: MutableSet<out Annotation>, moshi: Moshi): JsonAdapter<*>? {
+        if (type !is ParameterizedType || List::class.java != type.rawType) return null
+        if (type.actualTypeArguments[0] != Pair::class.java) return null
+
+        val listType = Types.newParameterizedType(List::class.java, Map::class.java, String::class.java)
+        val listAdapter = moshi.adapter<List<Map<String, String>>>(listType)
+
+        val mapType = Types.newParameterizedType(MutableMap::class.java, String::class.java, String::class.java)
+        val mapAdapter = moshi.adapter<Map<String, String>>(mapType)
+
+        return PairAdapter(listAdapter, mapAdapter)
+    }
+
+    private class PairAdapter(
+        private val listAdapter: JsonAdapter<List<Map<String, String>>>,
+        private val mapAdapter: JsonAdapter<Map<String, String>>,
+    ) : JsonAdapter<List<Pair<String, String>>>() {
+
+        override fun toJson(writer: JsonWriter, value: List<Pair<String, String>>?) {
+            writer.beginArray()
+            value?.forEach {
+                writer.beginObject()
+                writer.name("first").value(it.first)
+                writer.name("second").value(it.second)
+                writer.endObject()
+            }
+            writer.endArray()
+        }
+
+        override fun fromJson(reader: JsonReader): List<Pair<String, String>>? {
+            return if (reader.peek() == JsonReader.Token.BEGIN_OBJECT) deserializeMoshiMap(reader)
+            else deserializeGsonPair(reader)
+        }
+
+        // for compatibility with 0.21.0
+        private fun deserializeMoshiMap(reader: JsonReader): List<Pair<String, String>>? {
+            val map = mapAdapter.fromJson(reader) ?: return null
+
+            return map.entries.map {
+                it.key to it.value
+            }
+        }
+
+        private fun deserializeGsonPair(reader: JsonReader): List<Pair<String, String>>? {
+            val list = listAdapter.fromJson(reader) ?: return null
+
+            require(list.size == 2 || list.isEmpty()) {
+                "pair with more or less than two elements: $list"
+            }
+
+            return list.map {
+                it["first"].orEmpty() to it["second"].orEmpty()
+            }
+        }
+    }
+}
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 09f44931..271eac7f 100644
--- a/app/src/main/play/release-notes/pl-PL/default.txt
+++ b/app/src/main/play/release-notes/pl-PL/default.txt
@@ -1,4 +1,4 @@
-Wersja 0.21.0
+Wersja 0.21.1
 - naprawiliśmy logowanie do tarnowskiego dziennika
 - naprawiliśmy wyświetlanie podsumowania punktów klasy
 - dodaliśmy skróty aplikacji
diff --git a/app/src/test/java/io/github/wulkanowy/data/db/ConvertersTest.kt b/app/src/test/java/io/github/wulkanowy/data/db/ConvertersTest.kt
new file mode 100644
index 00000000..50741b7a
--- /dev/null
+++ b/app/src/test/java/io/github/wulkanowy/data/db/ConvertersTest.kt
@@ -0,0 +1,25 @@
+package io.github.wulkanowy.data.db
+
+import org.junit.Assert.assertEquals
+import org.junit.Test
+
+class ConvertersTest {
+
+    @Test
+    fun stringPairListToJson() {
+        assertEquals(Converters().stringPairListToJson(listOf("aaa" to "bbb", "ccc" to "ddd")), "[{\"first\":\"aaa\",\"second\":\"bbb\"},{\"first\":\"ccc\",\"second\":\"ddd\"}]")
+        assertEquals(Converters().stringPairListToJson(listOf()), "[]")
+    }
+
+    @Test
+    fun jsonToStringPairList() {
+        assertEquals(Converters().jsonToStringPairList("[{\"first\":\"aaa\",\"second\":\"bbb\"},{\"first\":\"ccc\",\"second\":\"ddd\"}]"), listOf("aaa" to "bbb", "ccc" to "ddd"))
+        assertEquals(Converters().jsonToStringPairList("[]"), listOf<Pair<String, String>>())
+    }
+
+    @Test
+    fun jsonToStringPairList_0210() {
+        assertEquals(Converters().jsonToStringPairList("{\"aaa\":\"bbb\",\"ccc\":\"ddd\"}"), listOf("aaa" to "bbb", "ccc" to "ddd"))
+        assertEquals(Converters().jsonToStringPairList("{}"), listOf<Pair<String, String>>())
+    }
+}