--- a/src/Makefile
+++ b/src/Makefile
@@ -147,17 +147,6 @@ endif
 # Flags to enable software debugging (slow down the code!).
 DEBUG_CFLAGS = -pedantic -Dcimg_verbosity=3 -Dcimg_strict_warnings -g -fsanitize=address # -fsanitize=thread # -fsanitize=undefined # Removed '-ansi' as it (silently) disables c++11.
 
-# Flags to enable optimizations.
-ifeq ($(notdir $(CXX)),g++)
-OPT_CFLAGS = -O3 -mtune=generic # -Ofast -march=native
-else
-ifeq ($(notdir $(CXX)),icpc)
-OPT_CFLAGS = -fast
-else
-OPT_CFLAGS = -O3
-endif
-endif
-
 # Flags to enable parallel processing.
 PARALLEL_CFLAGS = -Dgmic_is_parallel
 ifneq ($(OS),Windows)
