diff --git a/unit_tests/Makefile b/unit_tests/Makefile
index ba87b72fbf..f3e4e08f8f 100644
--- a/unit_tests/Makefile
+++ b/unit_tests/Makefile
@@ -12,7 +12,8 @@ ifeq ($(USE_OPT),)
 #
 # -O2 is needed for mingw, without it there is a linking issue to isnanf?!?!
   #USE_OPT = $(RFLAGS) -O2 -fgnu89-inline -ggdb -fomit-frame-pointer -falign-functions=16 -std=gnu99 -Werror-implicit-function-declaration -Werror -Wno-error=pointer-sign -Wno-error=unused-function -Wno-error=unused-variable -Wno-error=sign-compare -Wno-error=unused-parameter -Wno-error=missing-field-initializers
-  USE_OPT = -c -Wall -O0 -ggdb -g3 -Werror=missing-field-initializers
+  USE_OPT = -c -Wall -O0 -ggdb -g3
+  USE_OPT += -Werror=missing-field-initializers
 endif
 
 ifeq ($(CCACHE_DIR),)