diff --git a/Makefile.conf b/Makefile.conf
index 15c9dde..e9f2627 100644
--- a/Makefile.conf
+++ b/Makefile.conf
@@ -62,7 +62,7 @@ ifeq ($(DEBUG),1)
     CXXFLAGS+=-g
 else
     $(info Release Build (set DEBUG=1 for debug build))
-    CXXFLAGS+=-DNDEBUG=1
+    CXXFLAGS+=-DNDEBUG=1 -O3
 endif
 
 ### YML_PATH is needed in the environment of every call to a program of the YML2 distribution