diff --git a/Makefile b/Makefile
index 19dbad6..8afcf11 100644
--- a/Makefile
+++ b/Makefile
@@ -17,7 +17,7 @@ ifneq (, $(shell which pdflatex))
 else
 	@echo Build using Docker image.
 	docker run --rm -i \
-		--user $(id -u ${USER}):$(id -g ${USER}) \
+		--user $$(id -u):$$(id -g) \
 		--net=none \
 		--read-only \
 		-v $(PWD):/data \
diff --git a/README.md b/README.md
index 68a3fac..eea0791 100644
--- a/README.md
+++ b/README.md
@@ -14,7 +14,7 @@ pdflatex aaronrobson-cv.tex
 #### Using docker
 ```sh
 docker run --rm -i \
-    --user $(id -u ${USER}):$(id -g ${USER}) \
+    --user $(id -u):$(id -g) \
     --net=none \
     --read-only \
     -v $(pwd):/data \