diff --git a/src/mk/Darwin b/src/mk/Darwin
index 8d5e8858..06dd6b5e 100644
--- a/src/mk/Darwin
+++ b/src/mk/Darwin
@@ -2,6 +2,7 @@ include $(depth)/mk/commondefs
 include $(depth)/mk/localdefs
 
 ALL_CXXFLAGS = $(CXXFLAGS) $(COMMONCXXFLAGS) $(LOCALCXXFLAGS) \
+           -DPUTENV_ARG_NOT_CONST \
 	   -DHAVE_VASPRINTF=1 \
 	   -DHAVE_MKDTEMP=1