diff --git a/Makefile b/Makefile
index 6ccda262..3670143f 100644
--- a/Makefile
+++ b/Makefile
@@ -43,7 +43,7 @@ PATH       := $(PREFIX)/$(BUILD)/bin:$(PREFIX)/bin:$(PATH)
 
 # use a minimal whitelist of safe environment variables
 ENV_WHITELIST := PATH LANG MAKE% MXE% %PROXY %proxy
-unexport $(filter-out $(ENV_WHITELIST),$(shell env | $(SED) -n 's,\(.*\)=.*,\1,p'))
+unexport $(filter-out $(ENV_WHITELIST),$(shell env | cut -d '=' -f1))
 
 SHORT_PKG_VERSION = \
     $(word 1,$(subst ., ,$($(1)_VERSION))).$(word 2,$(subst ., ,$($(1)_VERSION)))