diff --git a/src/main/java/org/jenkinsci/remoting/engine/JnlpAgentEndpointResolver.java b/src/main/java/org/jenkinsci/remoting/engine/JnlpAgentEndpointResolver.java
index fa38b6451..562454669 100644
--- a/src/main/java/org/jenkinsci/remoting/engine/JnlpAgentEndpointResolver.java
+++ b/src/main/java/org/jenkinsci/remoting/engine/JnlpAgentEndpointResolver.java
@@ -428,8 +428,8 @@ private static List<String> header(@Nonnull HttpURLConnection connection, String
         Map<String, List<String>> headerFields = connection.getHeaderFields();
         for (String headerName : headerNames) {
             for (String headerField : headerFields.keySet()) {
-                if (headerField.equalsIgnoreCase(headerName)) {
-                    return headerFields.get(headerName);
+                if (headerField != null && headerField.equalsIgnoreCase(headerName)) {
+                    return headerFields.get(headerField);
                 }
             }
         }