diff --git a/qa/ganeti-qa.py b/qa/ganeti-qa.py
index d90ff6b5b98880b9302d2c9ec203586071840c67..0925796a6563119882da45453d7236cee62a931b 100755
--- a/qa/ganeti-qa.py
+++ b/qa/ganeti-qa.py
@@ -317,6 +317,8 @@ def main():
         try:
           instance = RunTest(func, pnode, snode)
           RunCommonInstanceTests(instance)
+          if qa_config.TestEnabled('instance-convert-disk'):
+            RunTest(qa_instance.TestInstanceConvertDisk, instance, snode)
           RunExportImportTests(instance, pnode)
           RunHardwareFailureTests(instance, pnode, snode)
           RunTest(qa_instance.TestInstanceRemove, instance)
diff --git a/qa/qa-sample.json b/qa/qa-sample.json
index a150b37d783965ae37da1ee396dfda681a6ee261..8f6f4db886f8a9673adca5fea688ed1bf77b4a80 100644
--- a/qa/qa-sample.json
+++ b/qa/qa-sample.json
@@ -62,6 +62,7 @@
 
     "instance-add-plain-disk": true,
     "instance-add-drbd-disk": true,
+    "instance-convert-disk": true,
 
     "instance-automatic-restart": false,
     "instance-consecutive-failures": false,
diff --git a/qa/qa_instance.py b/qa/qa_instance.py
index 8552e2686d3a712e074f02d66cb598940634f141..fcd54d223bbbd5c1227ae9b2403d66d1e5bb6526 100644
--- a/qa/qa_instance.py
+++ b/qa/qa_instance.py
@@ -209,6 +209,17 @@ def TestInstanceModify(instance):
                           utils.ShellQuoteArgs(cmd)).wait(), 0)
 
 
+def TestInstanceConvertDisk(instance, snode):
+  """gnt-instance modify -t"""
+  master = qa_config.GetMasterNode()
+  cmd = ['gnt-instance', 'modify', '-t', 'plain', instance['name']]
+  AssertEqual(StartSSH(master['primary'],
+                       utils.ShellQuoteArgs(cmd)).wait(), 0)
+  cmd = ['gnt-instance', 'modify', '-t', 'drbd', '-n', snode, instance['name']]
+  AssertEqual(StartSSH(master['primary'],
+                       utils.ShellQuoteArgs(cmd)).wait(), 0)
+
+
 def TestInstanceList():
   """gnt-instance list"""
   master = qa_config.GetMasterNode()