diff --git a/Makefile b/Makefile
index fe4a9cb..0653cb4 100644
--- a/Makefile
+++ b/Makefile
@@ -1,3 +1,3 @@
 .PHONY: proto
 proto:
-	protoc -I. -I$(GOPATH)/src/googleapis --swagger_out=logtostderr=true:. --grpc-gateway_out=logtostderr=true:. --go_out=plugins=grpc:proto/ proto/*.proto 
\ No newline at end of file
+	protoc -I. -I${GOPATH}/src/googleapis --swagger_out=logtostderr=true:. --grpc-gateway_out=logtostderr=true:. --go_out=plugins=grpc:proto/ proto/*.proto 
\ No newline at end of file