diff --git a/tangent/transformers.py b/tangent/transformers.py
index 3d6e27f..51f3e99 100644
--- a/tangent/transformers.py
+++ b/tangent/transformers.py
@@ -272,7 +272,7 @@ def visit(self, node):
       if not node.orelse:
         return
       else:
-        node.test = gast.UnaryOp(op=gast.Not, operand=node.test)
+        node.test = gast.UnaryOp(op=gast.Not(), operand=node.test)
         node.body, node.orelse = node.orelse, node.body
     elif isinstance(node, (gast.While, gast.For)) and not node.body:
       return node.orelse