diff --git a/src/sql/kernel/qsqlerror.cpp b/src/sql/kernel/qsqlerror.cpp
index 2f51debdd0..5e69778a2a 100644
--- a/src/sql/kernel/qsqlerror.cpp
+++ b/src/sql/kernel/qsqlerror.cpp
@@ -151,9 +151,13 @@ QSqlError::QSqlError(const QSqlError& other)
 
 QSqlError& QSqlError::operator=(const QSqlError& other)
 {
-    if (d)
+    if (&other == this)
+        return *this;
+    if (d && other.d)
         *d = *other.d;
-    else
+    else if (d)
+        *d = QSqlErrorPrivate();
+    else if (other.d)
         d = new QSqlErrorPrivate(*other.d);
     return *this;
 }
diff --git a/tests/auto/corelib/io/qfile/tst_qfile.cpp b/tests/auto/corelib/io/qfile/tst_qfile.cpp
index bdfcc2d350..188e3fdc25 100644
--- a/tests/auto/corelib/io/qfile/tst_qfile.cpp
+++ b/tests/auto/corelib/io/qfile/tst_qfile.cpp
@@ -27,6 +27,8 @@
 **
 ****************************************************************************/
 
+#define _CRT_SECURE_NO_WARNINGS 1
+
 #include <QTest>
 #include <QScopedValueRollback>
 #include <qplatformdefs.h>
diff --git a/tests/auto/corelib/io/qipaddress/tst_qipaddress.cpp b/tests/auto/corelib/io/qipaddress/tst_qipaddress.cpp
index 5f99cec3af..60b0c697c5 100644
--- a/tests/auto/corelib/io/qipaddress/tst_qipaddress.cpp
+++ b/tests/auto/corelib/io/qipaddress/tst_qipaddress.cpp
@@ -26,6 +26,8 @@
 **
 ****************************************************************************/
 
+#define _CRT_SECURE_NO_WARNINGS 1
+
 #include <QtCore/QString>
 #include <QTest>
 #include <QtCore/private/qipaddress_p.h>