diff --git a/src/network/access/qnetworkrequest.cpp b/src/network/access/qnetworkrequest.cpp
index 3a3e24b80b..00d5b81413 100644
--- a/src/network/access/qnetworkrequest.cpp
+++ b/src/network/access/qnetworkrequest.cpp
@@ -752,7 +752,8 @@ static QByteArray headerValue(QNetworkRequest::KnownHeaders header, const QVaria
 
 static QNetworkRequest::KnownHeaders parseHeaderName(const QByteArray &headerName)
 {
-    // headerName is not empty here
+    if (headerName.isEmpty())
+        return QNetworkRequest::KnownHeaders(-1);
 
     switch (tolower(headerName.at(0))) {
     case 'c':