diff --git a/src/corelib/io/qiodevice.cpp b/src/corelib/io/qiodevice.cpp
index 89987bc64a..8e1b2d5d0c 100644
--- a/src/corelib/io/qiodevice.cpp
+++ b/src/corelib/io/qiodevice.cpp
@@ -451,11 +451,17 @@ void QIODevice::setOpenMode(OpenMode openMode)
     otherwise the \l Text flag is removed. This feature is useful for classes
     that provide custom end-of-line handling on a QIODevice.
 
+    The IO device should be opened before calling this function.
+
     \sa open(), setOpenMode()
  */
 void QIODevice::setTextModeEnabled(bool enabled)
 {
     Q_D(QIODevice);
+    if (!isOpen()) {
+        qWarning("QIODevice::setTextModeEnabled: The device is not open");
+        return;
+    }
     if (enabled)
         d->openMode |= Text;
     else