diff --git a/Makefile b/Makefile
index b1c60ce..7e0cf68 100644
--- a/Makefile
+++ b/Makefile
@@ -1,13 +1,14 @@
-.PHONY: all xpi test
+.PHONY: all xpi test check-env check-jwt-issuer check-jwt-secret
 
 SOURCES := $(wildcard *.js) $(wildcard lib/*.js)
 INSTALL_RDF_PATCH := $(abspath install.rdf.patch)
+UNSIGNED_XPI := zotero-voyant-export.xpi
 
 all: xpi
 
-xpi: zotero-voyant-export.xpi
+xpi: $(UNSIGNED_XPI)
 
-zotero-voyant-export.xpi: $(SOURCES) $(INSTALL_RDF_PATCH)
+$(UNSIGNED_XPI): $(SOURCES) $(INSTALL_RDF_PATCH)
 	rm -f $@
 	jpm xpi --dest-dir /tmp
 	rm -rf /tmp/zotero-voyant-export
@@ -18,3 +19,18 @@ zotero-voyant-export.xpi: $(SOURCES) $(INSTALL_RDF_PATCH)
 
 test:
 	jpm test -b "/Applications/Nightly.app"
+
+check-env: check-jwt-issuer check-jwt-secret
+
+check-jwt-issuer:
+ifndef JWT_ISSUER
+	$(error JWT_ISSUER is undefined)
+endif
+
+check-jwt-secret:
+ifndef JWT_SECRET
+	$(error JWT_SECRET is undefined)
+endif
+
+sign: $(UNSIGNED_XPI) check-env
+	jpm sign --api-key $(JWT_ISSUER) --api-secret $(JWT_SECRET) --xpi $<
diff --git a/README.md b/README.md
index e44c1d9..172493e 100644
--- a/README.md
+++ b/README.md
@@ -40,6 +40,9 @@ for an indication of what has been/will be done. Help is very welcome!
 
 Run `make` to create a new XPI.
 
+Signing can be done with `make sign`, if you have the `JWT_ISSUER` and
+`JWT_SECRET` environment variables set.
+
 ### Tests
 
 Run the tests using Firefox Nightly, e.g.:
diff --git a/package.json b/package.json
index dddb06d..6b136d7 100644
--- a/package.json
+++ b/package.json
@@ -8,6 +8,7 @@
   "engines": {
     "firefox": ">=38.0a1"
   },
+  "updateURL": "https://corajr.github.io/zotero-voyant-export/update.rdf",
   "license": "AGPL-3.0",
   "keywords": [
     "jetpack"