diff --git a/llvm/utils/buildit/GNUmakefile b/llvm/utils/buildit/GNUmakefile
index dbdb930ae1be..08904e656352 100644
--- a/llvm/utils/buildit/GNUmakefile
+++ b/llvm/utils/buildit/GNUmakefile
@@ -78,7 +78,7 @@ EmbeddedHosted:
 # (e.g., tblgen), so set it here.
 EmbeddedSim:
 	export MACOSX_DEPLOYMENT_TARGET=`sw_vers -productVersion`; \
-	$(MAKE) IOS_SIM_BUILD=yes PREFIX=/usr install
+	$(MAKE) IOS_SIM_BUILD=yes PREFIX=$(SDKROOT)/usr install
 
 # installhdrs does nothing, because the headers aren't useful until
 # the compiler is installed.