diff --git a/core/build.gradle b/core/build.gradle
index 41326f5b6..7b6da8811 100644
--- a/core/build.gradle
+++ b/core/build.gradle
@@ -17,7 +17,7 @@ android {
         release {
             shrinkResources true
             minifyEnabled true
-            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
+            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
         }
     }
 }
diff --git a/core/proguard-rules.pro b/core/proguard-rules.pro
index 9e85b4582..807fedc79 100644
--- a/core/proguard-rules.pro
+++ b/core/proguard-rules.pro
@@ -3,4 +3,9 @@
 -keepnames class com.watabou.** { *; }
 -keep class com.shatteredpixel.shatteredpixeldungeon { *; }
 -keep class com.watabou.noosa.game { *; }
--keepattributes SourceFile,LineNumberTable
\ No newline at end of file
+-keepattributes SourceFile,LineNumberTable
+
+# overrides default in proguard-android-optimize.txt, which is:
+# -optimizations !code/simplification/arithmetic,!code/simplification/cast,!field/*,!class/merging/*
+# This is because code/simplification/arithmetic is safe to use on android 2.0+
+-optimizations !code/simplification/cast,!field/*,!class/merging/*
\ No newline at end of file