diff --git a/CMakeLists.txt b/CMakeLists.txt
index e5a46381..8a7cc5e0 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -178,7 +178,7 @@ endif()
 
 # Compiler flags
 if(CMAKE_C_COMPILER_ID MATCHES "AppleClang|Clang|GNU")
-  list(APPEND mi_cflags -Wall -Wextra -Wno-unknown-pragmas -fvisibility=hidden   $<$<CONFIG:RELEASE>:-O3>)
+  list(APPEND mi_cflags -Wall -Wextra -Wno-unknown-pragmas -fvisibility=hidden)
   if(NOT MI_USE_CXX)
     list(APPEND mi_cflags -Wstrict-prototypes)
   endif()