diff --git a/make/defs.mk b/make/defs.mk
index eddfe6a7..96e996a7 100644
--- a/make/defs.mk
+++ b/make/defs.mk
@@ -29,13 +29,13 @@ ifneq ($(wildcard pre-local.mk),)
 endif
 
 # ----- executables
-SED                   := /usr/bin/sed
+SED                   := $(shell which sed)
 CAT                   := /bin/cat
 SHELL                 ?= /bin/bash
 BROWSER               ?= firefox
-RM                    := /usr/bin/rm
+RM                    := $(shell which rm)
 AR                     = /usr/bin/ar
-PWD                   := /usr/bin/pwd
+PWD                   := $(shell which pwd)
 BIN_INSTALL           := /usr/bin/install
 SUDO                  ?= /usr/bin/sudo