diff --git a/src/gui/image/qimage.cpp b/src/gui/image/qimage.cpp
index 887a7c29eb1..6699e516a0a 100644
--- a/src/gui/image/qimage.cpp
+++ b/src/gui/image/qimage.cpp
@@ -4565,7 +4565,7 @@ bool QImageData::convertInPlace(QImage::Format newFormat, Qt::ImageConversionFla
         return true;
 
     // No in-place conversion if we have to detach
-    if (ref.load() > 1)
+    if (ref.load() > 1 || ro_data)
         return false;
 
     const InPlace_Image_Converter *const converterPtr = &qimage_inplace_converter_map[format][newFormat];
diff --git a/tests/auto/gui/image/qimage/tst_qimage.cpp b/tests/auto/gui/image/qimage/tst_qimage.cpp
index ed1d9156708..e8da3263aef 100644
--- a/tests/auto/gui/image/qimage/tst_qimage.cpp
+++ b/tests/auto/gui/image/qimage/tst_qimage.cpp
@@ -2492,6 +2492,19 @@ void tst_QImage::inplaceConversion()
     }
     if (image.depth() == imageConverted.depth())
         QCOMPARE(imageConverted.constScanLine(0), originalPtr);
+
+    {
+        // Test attempted inplace conversion of images created on existing, readonly buffer
+        static const quint32 readOnlyData[] = { 0x00010203U, 0x04050607U, 0x08091011U, 0x12131415U };
+
+        QImage roImage((const uchar *)readOnlyData, 2, 2, format);
+        QImage inplaceConverted = std::move(roImage).convertToFormat(dest_format);
+
+        QImage roImage2((const uchar *)readOnlyData, 2, 2, format);
+        QImage normalConverted = roImage2.convertToFormat(dest_format);
+
+        QCOMPARE(normalConverted, inplaceConverted);
+    }
 #endif
 }