diff --git a/app/build.gradle b/app/build.gradle
index a3b25d64b..99e02e763 100755
--- a/app/build.gradle
+++ b/app/build.gradle
@@ -14,16 +14,17 @@ android {
 
     buildTypes {
         release {
-            minifyEnabled false
+            minifyEnabled true
+            //shrinkResources true todo: test before enabling, a lot of resources are accessed via getIdentifier and possibly not all have been marked with "keep"
             debuggable false
             jniDebuggable false
             renderscriptDebuggable false
-            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
+            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro', 'src/main/proguard.flags'
         }
         debug {
-            minifyEnabled false
+            minifyEnabled true
             jniDebuggable false
-            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
+            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro', 'src/main/proguard.flags'
             applicationIdSuffix ".debug"
         }
         archivesBaseName = "openboard_" + defaultConfig.versionName
diff --git a/app/src/main/java/org/dslul/openboard/inputmethod/latin/settings/AppearanceSettingsFragment.kt b/app/src/main/java/org/dslul/openboard/inputmethod/latin/settings/AppearanceSettingsFragment.kt
index 8b560f669..2e43e96ad 100644
--- a/app/src/main/java/org/dslul/openboard/inputmethod/latin/settings/AppearanceSettingsFragment.kt
+++ b/app/src/main/java/org/dslul/openboard/inputmethod/latin/settings/AppearanceSettingsFragment.kt
@@ -50,7 +50,7 @@ class AppearanceSettingsFragment : SubScreenFragment() {
         needsReload = false
     }
 
-    override fun onSharedPreferenceChanged(prefs: SharedPreferences, key: String) {
+    override fun onSharedPreferenceChanged(prefs: SharedPreferences?, key: String?) {
         super.onSharedPreferenceChanged(prefs, key)
         needsReload = true // may not always be the necessary, but that's ok
     }