diff --git a/CMakeLists.txt b/CMakeLists.txt
index 3ed9f6b56..c1517e93c 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -271,7 +271,7 @@ ELSEIF( CMAKE_COMPILER_IS_MINGW )
     SET(CMAKE_CXX_FLAGS "-std=c++11 ${CMAKE_CXX_FLAGS}")
     SET(CMAKE_C_FLAGS "-fPIC ${CMAKE_C_FLAGS}")
   ENDIF()
-  SET(CMAKE_CXX_FLAGS "-fvisibility=hidden -fno-strict-aliasing -Wall -Wno-long-long -Wa,-mbig-obj ${CMAKE_CXX_FLAGS}")
+  SET(CMAKE_CXX_FLAGS "-fvisibility=hidden -fno-strict-aliasing -Wall -Wno-long-long -Wa,-mbig-obj -O3 ${CMAKE_CXX_FLAGS}")
   SET(CMAKE_C_FLAGS "-fno-strict-aliasing ${CMAKE_C_FLAGS}")
   ADD_DEFINITIONS( -U__STRICT_ANSI__ )
 ENDIF()