diff --git a/vertx-auth-common/src/main/java/io/vertx/ext/auth/impl/cose/CWK.java b/vertx-auth-common/src/main/java/io/vertx/ext/auth/impl/cose/CWK.java
index 6e290b406..2d3988c16 100644
--- a/vertx-auth-common/src/main/java/io/vertx/ext/auth/impl/cose/CWK.java
+++ b/vertx-auth-common/src/main/java/io/vertx/ext/auth/impl/cose/CWK.java
@@ -50,6 +50,9 @@ private NV(String name, String... pairs) {
       if (pairs == null || pairs.length == 0) {
         this.values = Collections.emptyMap();
       } else {
+        if (pairs.length % 2 != 0) {
+          throw new IllegalArgumentException("pairs must have even length");
+        }
         Map<String, String> tmp = new HashMap<>();
         for (int i = 0; i < pairs.length; i += 2) {
           tmp.put(pairs[i], pairs[i + 1]);