diff --git a/lib/query.py b/lib/query.py
index b922bf97440e2155f6f81f71df1b2393e38fe9a5..01b434b00b1112590d6016404a58ec8c1f64bb12 100644
--- a/lib/query.py
+++ b/lib/query.py
@@ -269,13 +269,16 @@ class _FilterHints:
     if op != qlang.OP_OR:
       self._NeedAllNames()
 
-  def NoteUnaryOp(self, op): # pylint: disable=W0613
+  def NoteUnaryOp(self, op, datakind): # pylint: disable=W0613
     """Called when handling an unary operation.
 
     @type op: string
     @param op: Operator
 
     """
+    if datakind is not None:
+      self._datakinds.add(datakind)
+
     self._NeedAllNames()
 
   def NoteBinaryOp(self, op, datakind, name, value):
@@ -557,19 +560,22 @@ class _FilterCompilerHelper:
     """
     assert op_fn is None
 
-    if hints_fn:
-      hints_fn(op)
-
     if len(operands) != 1:
       raise errors.ParameterError("Unary operator '%s' expects exactly one"
                                   " operand" % op)
 
     if op == qlang.OP_TRUE:
-      (_, _, _, retrieval_fn) = self._LookupField(operands[0])
+      (_, datakind, _, retrieval_fn) = self._LookupField(operands[0])
+
+      if hints_fn:
+        hints_fn(op, datakind)
 
       op_fn = operator.truth
       arg = retrieval_fn
     elif op == qlang.OP_NOT:
+      if hints_fn:
+        hints_fn(op, None)
+
       op_fn = operator.not_
       arg = self._Compile(operands[0], level + 1)
     else:
diff --git a/test/ganeti.query_unittest.py b/test/ganeti.query_unittest.py
index f1e848b60b8f95dbdb9e8dd0732f88ed36fb64e0..024102aac3982bfe5e0682f65704599859c0983b 100755
--- a/test/ganeti.query_unittest.py
+++ b/test/ganeti.query_unittest.py
@@ -1521,6 +1521,19 @@ class TestQueryFilter(unittest.TestCase):
     self.assertEqual(q.RequestedData(), set([DK_B]))
     self.assertEqual(q.Query(data), [[]])
 
+    # Data type in boolean operator
+    q = query.Query(fielddefs, [], namefield="name",
+                    qfilter=["?", "name"])
+    self.assertTrue(q.RequestedNames() is None)
+    self.assertEqual(q.RequestedData(), set([DK_A]))
+    self.assertEqual(q.Query(data), [[], [], []])
+
+    q = query.Query(fielddefs, [], namefield="name",
+                    qfilter=["!", ["?", "name"]])
+    self.assertTrue(q.RequestedNames() is None)
+    self.assertEqual(q.RequestedData(), set([DK_A]))
+    self.assertEqual(q.Query(data), [])
+
   def testFilterContains(self):
     fielddefs = query._PrepareFieldList([
       (query._MakeField("name", "Name", constants.QFT_TEXT, "Name"),