--- a/src/Makefile
+++ b/src/Makefile
@@ -117,17 +117,6 @@ endif
 # Flags to enable debugging.
 DEBUG_CFLAGS = -ansi -pedantic -Dcimg_verbosity=3 -g -fsanitize=address # -fsanitize=thread # -fsanitize=undefined #
 
-# Flags to enable optimizations.
-ifeq ($(notdir $(CC)),g++)
-OPT_CFLAGS = -O2 -mtune=generic
-else
-ifeq ($(notdir $(CC)),icpc)
-OPT_CFLAGS = -fast
-else
-OPT_CFLAGS = -O2
-endif
-endif
-
 # Flags to enable parallel processing.
 PARALLEL_CFLAGS = -Dgmic_is_parallel
 ifneq ($(OSTYPE),msys)
