diff --git a/src/corelib/text/qbytedata_p.h b/src/corelib/text/qbytedata_p.h
index 946f9155ffd..46eee13ccd4 100644
--- a/src/corelib/text/qbytedata_p.h
+++ b/src/corelib/text/qbytedata_p.h
@@ -105,6 +105,7 @@ public:
     // preferably use this function to read data.
     inline QByteArray read()
     {
+        Q_ASSERT(!isEmpty());
         squeezeFirst();
         bufferCompleteSize -= buffers.first().size();
         return buffers.takeFirst();