src/main/res/layout/toolbar.xml

@@ -6,6 +6,7 @@
     android:minHeight="?attr/actionBarSize"
     android:elevation="@dimen/toolbar_elevation"
     android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"
+    app:subtitleTextAppearance="@style/ToolbarSubtitleAppearance"
     app:popupTheme="?popupOverlayStyle"
     xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:app="http://schemas.android.com/apk/res-auto" />

src/main/res/values/styles.xml

@@ -51,6 +51,10 @@
         <item name="android:textSize">?TextSizeCaption</item>
     </style>
 
+    <style name="ToolbarSubtitleAppearance" parent="@style/TextAppearance.Widget.AppCompat.Toolbar.Subtitle">
+        <item name="android:textSize">12sp</item>
+    </style>
+
     <style name="Widget.Conversations.EditText" parent="Widget.AppCompat.EditText">
         <item name="android:textSize">?TextSizeInput</item>
     </style>