diff --git a/lib/CMakeLists.txt b/lib/CMakeLists.txt
index e550fee..9040c51 100644
--- a/lib/CMakeLists.txt
+++ b/lib/CMakeLists.txt
@@ -4,7 +4,7 @@ message( STATUS "*** CFLAGS \"" ${CMAKE_C_FLAGS} "\" from build environment will
 
 # Common x86/x86_64 cflags
 if( NOT NO_MARCH_NATIVE AND CMAKE_SYSTEM_PROCESSOR MATCHES "(x86)|(X86)|(amd64)|(AMD64)" )
-  set( CMAKE_C_FLAGS "-Ofast -march=native ${CMAKE_C_FLAGS}" )
+  set( CMAKE_C_FLAGS "-O3 -march=native ${CMAKE_C_FLAGS}" )
   message( STATUS "Using CFLAGS with  -march=native" )
   message( STATUS "*** ONLY USE THIS WHEN COMPILING ON THE MACHINE THAT WILL RUN UXPLAY" )
   message( STATUS "  run \"cmake -DNO_MARCH_NATIVE=ON\" to switch off this compiler option" )