diff --git a/INSTALL b/INSTALL
index 282f900c..bfb7f657 100755
--- a/INSTALL
+++ b/INSTALL
@@ -116,6 +116,7 @@ if [ `uname` = Darwin ]; then
 	*x86_64*)
 		echo "	x86-64 found."
 		echo "OBJTYPE=x86_64" >>$PLAN9/config
+		echo "CC9='xcrun --sdk macosx clang'" >>$PLAN9/config
 		;;
 	*i386*)
 		echo "	i386 found."