diff --git a/src/corelib/io/qtemporaryfile.cpp b/src/corelib/io/qtemporaryfile.cpp
index 55d13dad70..c016a622c7 100644
--- a/src/corelib/io/qtemporaryfile.cpp
+++ b/src/corelib/io/qtemporaryfile.cpp
@@ -284,8 +284,10 @@ createUnnamedFile(NativeFileHandle &file, QTemporaryFileName &tfn, quint32 mode,
         return CreateUnnamedFileStatus::NotSupported;
 
     const char *p = ".";
-    int lastSlash = tfn.path.lastIndexOf('/');
-    if (lastSlash != -1) {
+    QByteArray::size_type lastSlash = tfn.path.lastIndexOf('/');
+    if (lastSlash >= 0) {
+        if (lastSlash == 0)
+            lastSlash = 1;
         tfn.path[lastSlash] = '\0';
         p = tfn.path.data();
     }
diff --git a/tests/auto/corelib/io/qtemporaryfile/tst_qtemporaryfile.cpp b/tests/auto/corelib/io/qtemporaryfile/tst_qtemporaryfile.cpp
index 00417fffa0..cdf79760f6 100644
--- a/tests/auto/corelib/io/qtemporaryfile/tst_qtemporaryfile.cpp
+++ b/tests/auto/corelib/io/qtemporaryfile/tst_qtemporaryfile.cpp
@@ -517,6 +517,9 @@ void tst_QTemporaryFile::openOnRootDrives()
             QTemporaryFile file(driveInfo.filePath() + "XXXXXX.txt");
             file.setAutoRemove(true);
             QVERIFY(file.open());
+
+            QFileInfo fi(file.fileName());
+            QCOMPARE(fi.absoluteDir(), driveInfo.filePath());
         }
     }
 #if defined(Q_OS_WIN) && !defined(Q_OS_WINRT)