1 files changed, 8 insertions, 4 deletions
diff --git a/src/corelib/serialization/qjsonwriter.cpp b/src/corelib/serialization/qjsonwriter.cpp
index 32feb41183..012d3bea86 100644
--- a/src/corelib/serialization/qjsonwriter.cpp
+++ b/src/corelib/serialization/qjsonwriter.cpp
@@ -59,7 +59,6 @@ static inline uchar hexdig(uint u)
 
 static QByteArray escapedString(const QString &s)
 {
-    const uchar replacement = '?';
     QByteArray ba(s.length(), Qt::Uninitialized);
 
     uchar *cursor = reinterpret_cast<uchar *>(const_cast<char *>(ba.constData()));
@@ -112,9 +111,14 @@ static QByteArray escapedString(const QString &s)
             } else {
                 *cursor++ = (uchar)u;
             }
-        } else {
-            if (QUtf8Functions::toUtf8<QUtf8BaseTraits>(u, cursor, src, end) < 0)
-                *cursor++ = replacement;
+        } else if (QUtf8Functions::toUtf8<QUtf8BaseTraits>(u, cursor, src, end) < 0) {
+            // failed to get valid utf8 use JSON escape sequence
+            *cursor++ = '\\';
+            *cursor++ = 'u';
+            *cursor++ = hexdig(u>>12 & 0x0f);
+            *cursor++ = hexdig(u>>8 & 0x0f);
+            *cursor++ = hexdig(u>>4 & 0x0f);
+            *cursor++ = hexdig(u & 0x0f);
         }
     }