diff --git a/config.mk b/config.mk
index 05a25b5..7309b33 100644
--- a/config.mk
+++ b/config.mk
@@ -259,7 +259,7 @@ SEDOPT_windows=	-u
 # Colorize warnings, errors and progress information
 LINE_BUFFERED=--line-buffered
 COLOR_FILTER=   | grep $(LINE_BUFFERED) -v -e "^true &&" $(COLORIZE)
-COLORIZE= | sed $(SEDOPT_$(OS_NAME))                                                                        		\
+COLORIZE?= | sed $(SEDOPT_$(OS_NAME))                                                                        		\
             -e 's/^\(.*[,:(]\{1,\}[0-9]*[ :)]*\)\([Ww]arning\)/$(POS_COLOR)\1$(WRN_COLOR)\2$(DEF_COLOR)/g'  		\
             -e 's/^\(.*[,:(]\{1,\}[0-9]*[ :)]*\)\([Ee]rror\)/$(POS_COLOR)\1$(ERR_COLOR)\2$(DEF_COLOR)/g'    		\
             -e 's/^\(\[BEGIN\]\)\(.*\)$$/$(STEP_COLOR)\1\2$(CLR_EOLINE)$(DEF_COLOR)/g'        				\