2 files changed, 8 insertions, 2 deletions
diff --git a/src/corelib/json/qjson_p.h b/src/corelib/json/qjson_p.h
index 81439a00ce..8d6735273c 100644
--- a/src/corelib/json/qjson_p.h
+++ b/src/corelib/json/qjson_p.h
@@ -60,6 +60,7 @@
 #include <qatomic.h>
 #include <qstring.h>
 #include <qendian.h>
+#include <qnumeric.h>
 
 #include <limits.h>
 
diff --git a/src/corelib/json/qjsonwriter.cpp b/src/corelib/json/qjsonwriter.cpp
index 76f62241e3..c284f76cbb 100644
--- a/src/corelib/json/qjsonwriter.cpp
+++ b/src/corelib/json/qjsonwriter.cpp
@@ -169,9 +169,14 @@ static void valueToJson(const QJsonPrivate::Base *b, const QJsonPrivate::Value &
     case QJsonValue::Bool:
         json += v.toBoolean() ? "true" : "false";
         break;
-    case QJsonValue::Double:
-        json += QByteArray::number(v.toDouble(b));
+    case QJsonValue::Double: {
+        const double d = v.toDouble(b);
+        if (qIsFinite(d))
+            json += QByteArray::number(d);
+        else
+            json += "null"; // +INF || -INF || NaN (see RFC4627#section2.4)
         break;
+    }
     case QJsonValue::String:
         json += '"';
         json += escapedString(v.toString(b));