diff --git a/Makefile b/Makefile
index de1c7d9..9809a6e 100644
--- a/Makefile
+++ b/Makefile
@@ -12,16 +12,12 @@ self-signed-cert:
 	# make a self-signed cert
 
 secrets/jupyterhub.crt:
-	@if [ "${SECRETS_VOLUME}" = "" ]; then \
-		echo "Need an SSL certificate in secrets/jupyterhub.crt"; \
-		exit 1; \
-	fi
+	@echo "Need an SSL certificate in secrets/jupyterhub.crt"
+	@exit 1
 
 secrets/jupyterhub.key:
-	@if [ "${SECRETS_VOLUME}" = "" ]; then \
-		echo "Need an SSL key in secrets/jupyterhub.key"; \
-		exit 1; \
-	fi
+	@echo "Need an SSL key in secrets/jupyterhub.key"
+	@exit 1
 
 userlist:
 	@echo "Add usernames, one per line, to ./userlist, such as:"
@@ -29,7 +25,15 @@ userlist:
 	@echo "    wash"
 	@exit 1
 
-check-files: secrets/jupyterhub.crt secrets/jupyterhub.key userlist
+# Do not require cert/key files if SECRETS_VOLUME defined
+secrets_volume = $(shell echo $(SECRETS_VOLUME))
+ifeq ($(secrets_volume),)
+	cert_files=secrets/jupyterhub.crt secrets/jupyterhub.key
+else
+	cert_files=
+endif
+
+check-files: userlist $(cert_files)
 
 pull:
 	docker pull $(DOCKER_NOTEBOOK_IMAGE)