diff --git a/CMakeLists.txt b/CMakeLists.txt
index c4a4fd0..aa177cb 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -14,7 +14,7 @@ set(CPACK_PROJECT_VERSION ${PROJECT_VERSION})
 # otool -lV build/ml | grep stack
 
 # set(CMAKE_CXX_FLAGS "-Wall -Wextra")
-set(CMAKE_CXX_FLAGS_RELEASE "-O3")
+set(CMAKE_CXX_FLAGS_RELEASE "-O3 -DNDEBUG")
 
 include_directories(/usr/local/opt/openssl/include ${CMAKE_SOURCE_DIR}/clib ${CMAKE_SOURCE_DIR})
 
diff --git a/ml.h b/ml.h
index 63c4a9c..ed4ad7a 100644
--- a/ml.h
+++ b/ml.h
@@ -6,7 +6,11 @@
 #include <sstream>
 #include <exception>
 
-const std::string VERSION = "ml 0.4 (" __DATE__ " " __TIME__ ")";
+#ifdef NDEBUG
+const std::string VERSION = "ml 0.4 (" __DATE__ " " __TIME__ "), Release";
+#else
+const std::string VERSION = "ml 0.4 (" __DATE__ " " __TIME__ "), Debug";
+#endif
 
 const std::string STDLIB_LOADER =
 	 R"(