diff --git a/app/src/main/cpp/CMakeLists.txt b/app/src/main/cpp/CMakeLists.txt
index 3aea56c52..19612537a 100644
--- a/app/src/main/cpp/CMakeLists.txt
+++ b/app/src/main/cpp/CMakeLists.txt
@@ -1,7 +1,7 @@
 project(ehviewer)
 cmake_minimum_required(VERSION 3.4.1)
 
-set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -O3 -fvisibility=hidden -fvisibility-inlines-hidden -ffunction-sections -fdata-sections -flto \
+set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Ofast -fvisibility=hidden -fvisibility-inlines-hidden -ffunction-sections -fdata-sections -flto \
            -mllvm -polly \
            -mllvm -polly-run-dce \
            -mllvm -polly-run-inliner \