diff --git a/rdjson_formatter/rdjson_formatter.rb b/rdjson_formatter/rdjson_formatter.rb
index 9f077b3..68ae9bc 100755
--- a/rdjson_formatter/rdjson_formatter.rb
+++ b/rdjson_formatter/rdjson_formatter.rb
@@ -34,7 +34,7 @@
 
   package_name = advisory['module_name']
   title = advisory['title']
-  cve_id = advisory['cves']&.first || advisory['id']
+  cve_id = (advisory['cves']&.first || advisory['id'])&.to_s
   url = advisory['url']
   severity = advisory['severity'].to_s.downcase
 
diff --git a/test/rdjson_formatter/test.sh b/test/rdjson_formatter/test.sh
index 89e77ab..006c1fb 100755
--- a/test/rdjson_formatter/test.sh
+++ b/test/rdjson_formatter/test.sh
@@ -3,6 +3,10 @@
 set -eux
 CWD=$(pwd)
 
+compare_json() {
+  diff -u <(jq -S . "$1") <(jq -S . "$2")
+}
+
 cd ./test/rdjson_formatter/testdata
 
 yarn audit --json 2>/dev/null \
@@ -12,4 +16,15 @@ yarn audit --json 2>/dev/null \
   > result.out
 
 cd "${CWD}"
-diff -u ./test/rdjson_formatter/testdata/result.ok ./test/rdjson_formatter/testdata/result.out
+compare_json ./test/rdjson_formatter/testdata/result.ok ./test/rdjson_formatter/testdata/result.out
+
+cd ./test/rdjson_formatter/testdata
+
+ruby "${CWD}/rdjson_formatter/rdjson_formatter.rb" yarn.lock \
+  < advisory_without_cve.jsonl \
+  | jq . \
+  | sed -e "s!${CWD}/!!g" \
+  > advisory_without_cve.out
+
+cd "${CWD}"
+compare_json ./test/rdjson_formatter/testdata/advisory_without_cve.ok ./test/rdjson_formatter/testdata/advisory_without_cve.out
diff --git a/test/rdjson_formatter/testdata/advisory_without_cve.jsonl b/test/rdjson_formatter/testdata/advisory_without_cve.jsonl
new file mode 100644
index 0000000..0d2c577
--- /dev/null
+++ b/test/rdjson_formatter/testdata/advisory_without_cve.jsonl
@@ -0,0 +1 @@
+{"type":"auditAdvisory","data":{"advisory":{"id":1116454,"module_name":"minimist","severity":"moderate","title":"Prototype Pollution in minimist","url":"https://github.com/advisories/GHSA-vh95-rmgr-6w4m","recommendation":"Upgrade to version 0.2.1 or later","cves":[]}}}
diff --git a/test/rdjson_formatter/testdata/advisory_without_cve.ok b/test/rdjson_formatter/testdata/advisory_without_cve.ok
new file mode 100644
index 0000000..5998515
--- /dev/null
+++ b/test/rdjson_formatter/testdata/advisory_without_cve.ok
@@ -0,0 +1,26 @@
+{
+  "source": {
+    "name": "yarn audit",
+    "url": "https://github.com/yarnpkg/yarn"
+  },
+  "severity": "WARNING",
+  "diagnostics": [
+    {
+      "message": "[moderate] Prototype Pollution in minimist\nSolution: Upgrade to version 0.2.1 or later",
+      "location": {
+        "path": "yarn.lock",
+        "range": {
+          "start": {
+            "line": 5,
+            "column": 0
+          }
+        }
+      },
+      "severity": "WARNING",
+      "code": {
+        "value": "1116454",
+        "url": "https://github.com/advisories/GHSA-vh95-rmgr-6w4m"
+      }
+    }
+  ]
+}